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Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2018	Feb. 08, 2019	Jun. 29, 2018
Document And Entity Information [Abstract]
Document Type	10-K/A
Amendment Flag	true
Amendment Description	This Amendment No. 1 on Form 10-K/A amends the SPS Commerce, Inc. (the “Company”) Annual Report on Form 10-K for the fiscal year ending December 31, 2018, as filed with the Securities and Exchange Commission (“SEC”) on February 22, 2019 (the “Original Filing”). We are filing this Amendment No. 1 for the sole purpose of correcting a typographical error in Item 6. Selected Financial Data and Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations. Within the operating data table of Item 6, the table in footnote 3 of Item 6, and the reconciliation of net income to non-GAAP income per share table in Item 7, the Income tax effects of adjustments was inadvertently reported as $(4,468,000), with the corresponding Non-GAAP income with tax adjustments reported as $36,101,000 and the corresponding Non-GAAP income per share reported as $2.10 (basic) and $2.05 (diluted). The correct numbers are: •Income tax effects of adjustments: $(6,594,000) •Non-GAAP income: $33,975,000 •Non-GAAP income per share: $1.98 (basic) and $1.93 (diluted) The correct numbers appeared in our press release dated February 12, 2019, which was filed as Exhibit 99 to our Current Report on Form 10-K. This Form 10-K/A does not reflect events occurring after the Original Filing and does not modify or update in any way the disclosures contained in the Original Filing except as set forth above. Accordingly, this Amendment No. 1 should be read in conjunction with our filings with the SEC subsequent to the date of the Original Filing. As required by Rule 12b-15 under the Securities Exchange Act of 1934, new certificates of our principal executive officer and principal financial officer are being filed as exhibits to this Amendment No. 1 on Form 10-K/A.
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	SPSC
Entity Registrant Name	SPS COMMERCE INC
Entity Central Index Key	0001092699
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		17,760,003
Entity Public Float			$ 1.3

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 133,859	$ 123,127
Short-term investments	44,537	40,192
Accounts receivable, net	27,488	24,897
Deferred costs	34,502	29,966
Other current assets	9,229	6,149
Total current assets	249,615	224,331
PROPERTY AND EQUIPMENT, net	20,957	16,856
GOODWILL	69,658	51,613
INTANGIBLE ASSETS, net	22,741	16,529
INVESTMENTS		5,206
OTHER ASSETS
Deferred costs	10,973	9,967
Deferred income tax asset	10,456	13,697
Other assets	1,723	1,539
Total assets	386,123	339,738
CURRENT LIABILITIES
Accounts payable	4,440	4,463
Accrued compensation	20,415	15,228
Accrued expenses	4,558	4,712
Deferred revenue	25,328	17,863
Deferred rent	1,781	1,679
Total current liabilities	56,522	43,945
OTHER LIABILITIES
Deferred revenue	2,512	2,731
Deferred rent	5,371	3,064
Deferred income tax liability	1,376	1,887
Other non-current liabilities	1,368
Total liabilities	67,149	51,627
COMMITMENTS and CONTINGENCIES
STOCKHOLDERS’ EQUITY
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 0 shares issued and outstanding
Common stock, $0.001 par value; 55,000,000 shares authorized; 17,757,628 and 17,249,153 shares issued; and 17,345,736 and 17,127,006 outstanding, respectively	18	17
Treasury stock, at cost; 411,892 and 122,147 shares, respectively	(25,679)	(5,815)
Additional paid-in capital	332,592	301,863
Retained earnings (accumulated deficit)	15,261	(8,611)
Accumulated other comprehensive (loss) income	(3,218)	657
Total stockholders’ equity	318,974	288,111
Total liabilities and stockholders’ equity	$ 386,123	$ 339,738

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	55,000,000	55,000,000
Common stock, shares issued	17,757,628	17,249,153
Common stock, shares outstanding	17,345,736	17,127,006
Treasury stock, shares	411,892	122,147

Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenues	$ 248,240	$ 220,085	$ 193,153
Cost of revenues	81,748	73,625	64,346
Gross profit	166,492	146,460	128,807
Operating expenses
Sales and marketing	71,719	71,261	66,876
Research and development	22,087	23,183	21,981
General and administrative	41,862	37,461	28,827
Amortization of intangible assets	4,093	4,574	4,738
Total operating expenses	139,761	136,479	122,422
Income from operations	26,731	9,981	6,385
Other income (expense)
Interest income, net	2,329	1,032	601
Other income (expense), net	(720)	(320)	732
Total other income, net	1,609	712	1,333
Income before income taxes	28,340	10,693	7,718
Income tax expense	4,468	10,342	2,755
Net income	$ 23,872	$ 351	$ 4,963
Net income per share
Basic	$ 1.39	$ 0.02	$ 0.29
Diluted	$ 1.36	$ 0.02	$ 0.29
Weighted average common shares used to compute net income per share
Basic	17,196	17,183	16,947
Diluted	17,606	17,356	17,241
Other comprehensive income
Foreign currency translation adjustments	$ (3,999)	$ 3,944	$ 336
Unrealized gain (loss) on investments, net of tax of $132, $0 and ($5)	397		(9)
Reclassification of unrealized (gain) loss on investments into earnings, net of tax of ($91), $24 and $0	(273)	39
Comprehensive income	$ 19,997	$ 4,334	$ 5,290

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Unrealized gain( loss) on investments, tax	$ 132	$ 0	$ (5)
Reclassification of unrealized (gain) loss on investments into earnings, tax	$ (91)	$ 24	$ 0

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2015	$ 231,432	$ 17		$ 265,265	$ (30,202)	$ (3,648)
Beginning balance, shares at Dec. 31, 2015		16,723,994
Stock-based compensation	8,023			8,023
Exercise of stock options and issuance of restricted stock	4,303			4,303
Exercise of stock options and issuance of restricted stock, shares		279,841
Excess tax benefit of stock options exercised	4,070			4,070
Employee stock purchase plan	1,732			1,732
Employee stock purchase plan, shares		33,357
Stock issued for acquisition	2,922			2,922
Stock issued for acquisition, Shares		43,953
Net income	4,963				4,963
Foreign currency translation adjustments	336					336
Reclassification of gain (loss) on investments into earnings	18					18
Unrealized gain (loss) on investments, net of tax	(32)					(32)
Ending balance at Dec. 31, 2016	257,767	$ 17		286,315	(25,239)	(3,326)
Ending balance, shares at Dec. 31, 2016		17,081,145
Stock-based compensation	12,728			12,728
Exercise of stock options and issuance of restricted stock	1,410			1,410
Exercise of stock options and issuance of restricted stock, shares		135,906
Cumulative-effect adjustment for previously unrecognized excess tax benefits	16,277				16,277
Employee stock purchase plan	1,933			1,933
Employee stock purchase plan, shares		40,968
Retirement of escrow shares	(523)			(523)
Retirement of escrow shares, shares		(8,866)
Repurchases of common stock	(5,815)		$ (5,815)
Repurchases of common stock, shares		(122,147)	122,147
Net income	351				351
Foreign currency translation adjustments	3,944					3,944
Reclassification of gain (loss) on investments into earnings	39					39
Ending balance at Dec. 31, 2017	288,111	$ 17	$ (5,815)	301,863	(8,611)	657
Ending balance, shares at Dec. 31, 2017		17,127,006	122,147
Stock-based compensation	11,270			11,270
Exercise of stock options and issuance of restricted stock	14,344	$ 1		14,343
Exercise of stock options and issuance of restricted stock, shares		433,199
Employee stock purchase plan	1,745			1,745
Employee stock purchase plan, shares		34,798
Repurchases of common stock	(19,864)		$ (19,864)
Repurchases of common stock, shares		(289,745)	289,745
Stock issued for acquisition	3,371			3,371
Stock issued for acquisition, Shares		40,478
Net income	23,872				23,872
Foreign currency translation adjustments	(3,999)					(3,999)
Reclassification of gain (loss) on investments into earnings	(273)					(273)
Unrealized gain (loss) on investments, net of tax	397					397
Ending balance at Dec. 31, 2018	$ 318,974	$ 18	$ (25,679)	$ 332,592	$ 15,261	$ (3,218)
Ending balance, shares at Dec. 31, 2018		17,345,736	411,892

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income	$ 23,872	$ 351	$ 4,963
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes	2,798	9,616	(2,083)
Earn-out liability	94		(1,103)
Depreciation and amortization of property and equipment	8,593	7,208	6,598
Amortization of intangible assets	4,093	4,574	4,738
Provision for doubtful accounts	2,592	1,705	1,375
Stock-based compensation	12,510	12,728	8,023
Other, net	(364)	(15)
Changes in assets and liabilities, net of effects of acquisition
Accounts receivable	(4,569)	(5,586)	(3,735)
Deferred costs	(5,564)	(7,813)	(4,085)
Other current and non-current assets	(3,333)	393	(1,911)
Accounts payable	937	832	(382)
Accrued compensation	3,957	1,304	2,291
Accrued expenses	(135)	1,192	990
Deferred revenue	7,094	5,588	2,852
Deferred rent	2,440	(1,027)	234
Net cash provided by operating activities	55,015	31,050	18,765
Cash flows from investing activities
Purchases of property and equipment	(13,750)	(7,271)	(8,008)
Purchases of investments	(81,666)	(47,878)	(23,135)
Maturities of investments	82,224	33,029	15,018
Acquisition of business and intangible assets, net of cash acquired	(27,273)	(500)	(18,032)
Net cash used in investing activities	(40,465)	(22,620)	(34,157)
Cash flows from financing activities
Repurchases of common stock	(19,864)	(5,815)
Net proceeds from exercise of options to purchase common stock	14,344	1,410	4,303
Excess tax benefit from exercise of options to purchase common stock			4,070
Net proceeds from employee stock purchase plan	1,745	1,933	1,732
Net cash (used in) provided by financing activities	(3,775)	(2,472)	10,105
Effect of foreign currency exchange rate changes	(43)	1,292	(374)
Net increase (decrease) in cash and cash equivalents	10,732	7,250	(5,661)
Cash and cash equivalents at beginning of year	123,127	115,877	121,538
Cash and cash equivalents at end of year	133,859	123,127	115,877
Supplemental disclosure of cash flow information
Cash paid for income taxes, net	1,534	1,068	722
Non-cash financing activities:
Net purchases of property and equipment on account	405	$ 1,335
Common stock issued for business acquisitions	$ 3,371		$ 2,922

General

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

General

NOTE A – General

Business Description

SPS Commerce is a leading provider of cloud-based supply chain management solutions that make it easier for retailers, suppliers, distributors, and logistics firms to orchestrate the management of item data, order fulfillment, inventory control and sales analytics across all channels. Implementing and maintaining a suite of supply chain management capabilities is resource intensive and is not a core competency for most businesses. The solutions offered by SPS commerce eliminate the need for on-premise software and support staff by taking on that capability on the customer’s behalf. The solutions SPS Commerce provides allow our customers to increase their supply cycle agility, optimize their inventory levels and sell-through, reduce operational costs and gain increased visibility into customer orders, ensuring that suppliers, distributors, and logistics firms can satisfy exacting retailer requirements.

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of SPS Commerce, Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated in the consolidated financial statements.

Foreign Currency Translation

Assets and liabilities denominated in currencies other than the U.S. dollar are translated into U.S. dollars at the exchange rates in effect at the balance sheet date, with the resulting translation adjustments recorded as a separate component of accumulated other comprehensive loss. Income and expense accounts are translated at the average exchange rates during the year. Foreign currency transaction gains and losses, if any, are included in net income.

Use of Estimates

Preparing financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.

Business Combinations

We recognize the fair value of the assets acquired and the liabilities assumed at the acquisition date, separately from goodwill. Goodwill as of the acquisition date is measured as the excess of consideration transferred and the net of the acquisition date amounts of the assets acquired and the liabilities assumed.

Assets acquired include tangible and intangible assets. We use estimates and assumptions that we believe are reasonable as a part of the purchase price allocation, which includes the process to determine the value and useful lives of purchased intangible assets and the process to determine the value of any contingent consideration liabilities. We recorded the acquisition-date fair value of any contingent liabilities, such as earn-out provisions, as part of the consideration transferred. The earn-out liability fair value is subsequently remeasured at each reporting date. The Company evaluates each contingent consideration to determine the valuation approach. See Note B for valuation methods utilized in the fair value measurement as of the acquisition date and see Note E for valuation methods utilized in the fair value remeasurement as of the reporting date.

While we believe these estimates and assumptions are reasonable, they are inherently uncertain and subject to refinement. As a result, during the measurement period, which may be up to one year from the acquisition date, we may record adjustments to the fair value of the assets acquired and the liabilities assumed. Any such adjustments would be recorded as an offset to goodwill. Upon the conclusion of the measurement period or final determination of the fair values, whichever comes first, any subsequent adjustments would be recorded in our consolidated statements of comprehensive income.

Segment Information

We operate in and report on one segment, which is supply chain management solutions.

Risk and Uncertainties

We rely on hardware and software licensed from third parties to offer our on-demand solutions. Our management believes alternate sources are available; however, disruption or termination of these relationships could adversely affect our operating results in the near term.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk consist principally of cash and cash equivalents in financial institutions in excess of federally insured limits and trade accounts receivable. Cash investments are held with financial institutions that we believe are subject to minimal risk.

Cash and Cash Equivalents

Cash and cash equivalents consist of cash and highly liquid investments with original maturities of less than 90 days. Cash and cash equivalents are stated at fair value.

Investments

Management determines the appropriate classification of certificates of deposit and marketable securities at the time of purchase and reevaluates such determination at each balance sheet date. Securities are classified as available for sale and are carried at fair value, with the change in unrealized gains and losses, net of tax, reported as a separate component on the consolidated statements of comprehensive income. Fair value is determined based on quoted market rates when observable or utilizing data points that are observable, such as quoted prices, interest rates and yield curves. When a determination has been made that an other-than-temporary decline in fair value has occurred, the amount of the decline that is related to a credit loss is realized and is included in other income (expense), net in the consolidated statements of comprehensive income.

Fair Value of Financial Instruments

The carrying amounts of our financial instruments, which include cash, cash equivalents, accounts receivable, accounts payable and other accrued expenses, approximates fair value due to their short maturities. Marketable securities are recorded at fair value as further described in Note E.

Accounts Receivable

Accounts receivable are initially recorded upon the sale of solutions to customers. Credit is granted in the normal course of business without collateral. Accounts receivable are stated net of allowances for doubtful accounts, which represent estimated losses resulting from the inability of certain customers to make the required payments. When determining the allowances for doubtful accounts, we take several factors into consideration including the overall composition of the accounts receivable aging, our prior history of accounts receivable write-offs, the type of customers and our experience with specific customers. We write-off accounts receivable when they are determined to be uncollectible. Changes in the allowances for doubtful accounts are recorded as bad debt expense and are included in general and administrative expense in our consolidated statements of comprehensive income.

Property and Equipment

Property and equipment, including assets acquired under capital lease obligations, are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives when placed in service, which are:

Computer equipment and software: 2 to 3 years

Office equipment and furniture: 5 to 7 years

Leasehold improvements: the shorter of the useful life of the asset or the remaining term of the lease

Significant additions or improvements extending asset lives beyond one year are capitalized, while repairs and maintenance are charged to expense as incurred. We also capitalize and amortize eligible costs to acquire or develop external-use software that are incurred after technological feasibility has been established. The assets and related accumulated depreciation and amortization are adjusted for asset retirements and disposals with the resulting gain or loss included in our consolidated statements of comprehensive income.

Research and Development

Research and development costs primarily include maintenance and data conversion activities related to our cloud-based supply chain management solutions and are expensed as incurred.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of identifiable net assets acquired in business combinations. We test goodwill for impairment annually at November 30, or more frequently if events or changes in circumstances indicate that the asset might be impaired. The impairment test is conducted by comparing the fair value of the net assets with the carrying value of the reporting unit. Fair value is determined using the direct market observation of market price and outstanding equity of the reporting unit at the testing date. If the carrying value of the goodwill exceeds the fair value of the reporting unit, goodwill may be impaired. If this occurs, the fair value is then allocated to its assets and liabilities in a manner similar to a purchase price allocation in order to determine the implied fair value of goodwill. This implied fair value is then compared to the carrying amount of goodwill and, if it is less, we would recognize an impairment loss.

Intangible Assets

Assets acquired in business combinations may include identifiable intangible assets such as subscriber relationships and non-competition agreements. We recognize separately from goodwill the fair value of the identifiable intangible assets acquired. We have determined the fair value and useful lives of our purchased intangible assets using certain estimates and assumptions that we believe are reasonable.

The purchased intangible assets are being amortized on a straight-line basis over their estimated useful lives, which are three to ten years for subscriber relationships, two to five years for non-competition agreements and one to ten years for technology and other.

Internal-use Software Implementation Assets

Internal-use software implementation costs are capitalized assets included in Other Assets and relate to costs incurred during the application development stage for various internal-use software from hosting arrangements.

Capitalized implementation costs are recognized on a straight-line basis beginning when the application is ready for its intended use and ending on the expected termination date of the hosting arrangement, including consideration of the noncancelable contractual term and reasonably certain renewals.

The terms are between four and five years for our current hosting arrangements. Recognized expense is reported in general and administrative expense, which is where the hosting arrangement subscriptions are reported.

Impairment of Long-Lived Assets

We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. The carrying amount of a long-lived asset is not recoverable if the carrying amount of an asset group exceeds the sum of the undiscounted cash flows expected to result from the use and eventual disposition of the assets at the date it is tested for recoverability, whether in use or under development. An impairment loss is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value.

Revenue Recognition

Revenues are recognized when our services are made available to our customers, in an amount that reflects the consideration we are contractually and legally entitled to in exchange for those services.

We determine revenue recognition through the following steps:

Identification of the contract, or contracts, with a customer

Identification of the performance obligations in the contract

Determination of the transaction price

Allocation of the transaction price to the performance obligations in the contract

Recognition of revenue when, or as, we satisfy a performance obligation

See Note C for further descriptions of our revenue recognition policy.

Deferred Costs

Deferred costs consist of costs to obtain customer contracts, such as commissions paid to sales personnel and to third-party partners for customer referrals, and costs to fulfill customer contracts, such as customer implementation costs.

Sales commissions relating to recurring revenues are considered incremental and recoverable costs of obtaining a contract with our customer. These commissions are calculated based on estimated annual recurring revenue to be generated over the customer’s initial contract year. These costs are deferred and amortized over the expected period of benefit which we have determined to be two years. Amortization expense is included in sales and marketing expenses in the accompanying condensed consolidated statements of comprehensive income.

Stock-Based Compensation

We recognize the cost of all share-based payments to employees, including grants of employee stock options, in the financial statements based on the grant date fair value of those awards. This cost is recognized over the period for which an employee is required to provide service in exchange for the award.

In valuing share-based awards, judgment is required in determining the expected volatility of common stock and the expected term individuals will hold their share-based awards prior to exercising. The expected volatility of the options is based on the historical volatility of our common stock. The expected term of the options is based on the simplified method which does not consider historical employee exercise behavior. The valuation does not include a forfeiture estimate as we recognize forfeitures as they occur.

Income Taxes

We account for income taxes using the asset and liability method, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance when, in our judgement, there is a less than a 50% likelihood that the deferred tax asset will be utilized.

We assess our ability to realize our deferred tax assets at the end of each reporting period. Realization of our deferred tax assets is contingent upon future taxable earnings. Accordingly, this assessment requires estimates and judgment. If the estimates of future taxable income vary from actual results, our assessment regarding the realization of these deferred tax assets could change. Future changes in the estimated amount of deferred taxes expected to be realized will be reflected in our consolidated financial statements in the period the estimate is changed, with a corresponding adjustment to our operating results.

We recognize the financial statement benefit of a tax position only after determining that the relevant tax authority would “more likely than not” sustain the position following an audit. For tax positions meeting the “more likely than not” threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the relevant tax authority.

Net Income Per Share

Basic net income per share has been computed using the weighted average number of shares of common stock outstanding during each period. Diluted net income per share also includes the impact of our outstanding potential common shares, including options, restricted stock units and restricted stock awards. Potential common shares that are anti-dilutive are excluded from the calculation of diluted net income per share.

Recently Adopted Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Other Assets and Deferred Costs – Contracts with Customers (Subtopic 340-40), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance replaced most existing revenue recognition guidance in GAAP. Topic 606 also includes Subtopic 340-40, Other Assets and Deferred Costs – Contracts with Customers, which requires the deferral of incremental costs of obtaining a contract with a customer. Collectively, we refer to Topic 606 and Subtopic 340-40 as the “new standard”. These requirements are effective for annual reporting periods beginning after December 15, 2017, and interim periods within those annual periods.

We adopted the new standard effective January 1, 2018, on a retrospective basis. The new standard did not impact our recognition of the recurring revenue received from customers for our cloud-based supply chain solutions; however, the adoption of the new standard impacted our accounting for certain upfront set-up fees, the periods over which the related revenues are recognized and the timing of revenue recognition for these set-up fees. The adoption of the new standard also impacted our accounting for certain costs to obtain our contracts, specifically related to the periods over which commissions are recognized.

Selected audited consolidated balance sheet line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	December 31, 2017
	As previously
	reported			Adjustments			As adjusted
ASSETS
Deferred costs	$	25,091		$	4,875		$	29,966
Deferred costs, non-current		6,770			3,197			9,967
Deferred income tax asset		17,551			(3,854	)		13,697
LIABILITIES
Accrued compensation		15,886			(658	)		15,228
Deferred revenue		16,407			1,456			17,863
Deferred revenue, non-current		10,602			(7,871	)		2,731
STOCKHOLDERS’ EQUITY
Accumulated deficit		(19,902	)		11,291			(8,611	)

Selected audited consolidated statement of operations line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported		Adjustments			As adjusted
Revenues	$	193,295	$	(142	)	$	193,153
Operating expenses
Sales and marketing		65,886		990			66,876
Income from operations		7,517		(1,132	)		6,385
Income tax expense		3,140		(385	)		2,755
Net income	$	5,710	$	(747	)	$	4,963
Net income per share
Basic	$	0.34		(0.05	)	$	0.29
Diluted	$	0.33		(0.04	)	$	0.29

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Revenues	$	220,566		$	(481	)	$	220,085
Operating expenses
Sales and marketing		73,295			(2,034	)		71,261
Income from operations		8,428			1,553			9,981
Income tax expense		11,580			(1,238	)		10,342
Net income (loss)	$	(2,440	)	$	2,791		$	351
Net income (loss) per share
Basic	$	(0.14	)		0.16		$	0.02
Diluted	$	(0.14	)		0.16		$	0.02

Selected audited consolidated statement of cash flows line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income	$	5,710		$	(747	)	$	4,963
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		(1,698	)		(385	)		(2,083	)
Changes in assets and liabilities
Deferred costs		(4,964	)		879			(4,085	)
Accrued compensation		2,180			111			2,291
Deferred revenue		2,710			142			2,852
Net cash provided by operating activities		18,765			—			18,765

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income (loss)	$	(2,440	)	$	2,791		$	351
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		10,854			(1,238	)		9,616
Changes in assets and liabilities
Deferred costs		(6,548	)		(1,265	)		(7,813	)
Accrued compensation		2,073			(769	)		1,304
Deferred revenue		5,107			481			5,588
Net cash provided by operating activities		31,050			—			31,050

In January 2018, we adopted FASB ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as business acquisitions or as an asset acquisition. The new standard specifies the required inputs and processes that are necessary to be a business. The adoption of this standard impacted our accounting for business combinations. See Note B for additional information regarding business combinations.

In March 2018, we adopted FASB ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, which updates the income tax accounting in U.S. GAAP to reflect the SEC interpretive guidance released on December 22, 2017, when the Tax Act was signed into law. Additional information regarding the adoption of this standard is contained in Note M.

In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The standard is effective for interim and annual reporting periods beginning after December 15, 2019 and can be applied either prospectively to implementation costs incurred after the date of adoption or retrospectively to all arrangements, with early adoption permitted.

We early adopted ASU 2018-15 as of October 1, 2018, under the prospective method. Additional disclosure regarding capitalized implementation costs is included within Note I.

Accounting Pronouncements Not Yet Adopted

In February 2016, the FASB issued ASU 2016-02, Leases, which will supersede existing lease guidance and will require all leases with a term greater than 12 months to be recognized in the statements of financial position and eliminate current real estate-specific lease guidance, while maintaining substantially similar classification criteria for distinguishing between finance leases and operating leases. This standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted.

We adopted the new standard on January 1, 2019 and used the effective date as our date of initial application. Consequently, financial information will not be updated and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019.

The new standard provides several optional practical expedients in transition. For the fiscal period beginning January 1, 2019, we have made the following elections. We elected the “package of practical expedients,” which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct costs. We did not elect the use-of hindsight or the practical expedient pertaining to land easements; the latter not being applicable to us. The new standard also provided practical expedients for an entity’s ongoing accounting. We elected the short-term lease recognition exemption for all leases that qualify which means we have not recognized right-of-use (“ROU”) assets or lease liabilities for these leases, and this included not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. We also elected the practical expedient to not separate lease and non-lease components for all leases.

This standard has a material effect on our financial statements beginning January 1, 2019. The most significant effects relate to the recognition of approximately $15.0 million in ROU assets and $15.0 million additional lease liabilities on our balance sheet for our existing operating leases.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. The amendment in this update replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects expected credit losses on instruments within its scope, including trade receivables. This update is intended to provide financial statement users with more decision-useful information about the expected credit losses. This ASU is effective for annual periods and interim periods for those annual periods beginning after December 15, 2019. Entities may early adopt beginning after December 15, 2018. We are currently evaluating the impact of the adoption of ASU 2016-13 on our consolidated financial statements.

In February 2018, the FASB issued ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220), which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Act and requires certain disclosures regarding stranded tax effects in accumulated other comprehensive income. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted during interim or annual periods. We believe the adoption of this standard will not have a material impact on our consolidated financial statements.

Business Acquisitions

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Business Acquisitions

NOTE B – Business Acquisitions

EDIAdmin

On October 3, 2018, we completed our asset acquisition of EDIAdmin, a privately held company providing end-to-end integration solutions, featuring a dedicated Integration Platform as a Service (“iPaaS”) called Cloud Hybrid Integration Platform (“CHIP”) and collaborative managed services for leading systems and applications, both cloud and on-premise. Pursuant to the asset purchase agreement, we paid $7.5 million in cash to the owner of EDIAdmin. The purchase agreement also allowed the seller to receive up to $1.7 million in cash, which becomes payable in first quarter 2020 and 2021 contingent upon the completion of certain revenue milestones at December 31, 2019 and December 31, 2020. During the year ended December 31, 2018, we recognized other expense of $0.1 million in our consolidated statements of comprehensive income due to the remeasurement of the contingent liability. See Note E for further disclosures on the remeasurement of the contingent liability. The purchase accounting for the EDIAdmin acquisition is complete as of December 31, 2018.

Purchase Price Allocation

We accounted for the acquisition as a business combination. We allocated the purchase price to the tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values as of the acquisition date. We engaged a third-party valuation firm to assist us in the determination of the value of the purchased intangible assets and of the earn-out liability. The excess of the purchase price over the fair value of net tangible and identifiable intangible assets acquired was recorded as goodwill. Goodwill is attributed to a trained workforce and other buyer-specific value resulting from expected synergies, including long-term cost savings, which are not included in the fair values of identifiable assets.

The purchase price consisted of the following (in thousands):

Cash	$	7,461
Fair value of earn-out liability		1,274
	$	8,735

The final purchase price is subject to a net working capital adjustment to be determined by the sellers and us, pursuant to the terms of the purchase agreement.

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):

Current assets	$	631
Goodwill		4,871
Intangible assets		3,400
Current liabilities		(57	)
Deferred revenue		(110	)
	$	8,735

Purchased Intangible Assets

The following table summarizes the estimated fair value of the purchased intangible assets and their estimated useful lives:

	Estimated		Estimated
	Fair Value		Life
Purchased Intangible Assets	(in thousands)		(in years)
Subscriber relationships	$	600		10
Developed technology		2,800		10
Total	$	3,400

The purchased intangible assets are being amortized on a straight-line basis over their estimated useful lives. Amortization expense for the period from October 3, 2018 through December 31, 2018 was $0.1 million.

CovalentWorks

On December 18, 2018, we completed our asset acquisition of CovalentWorks, a privately held company providing cloud-based EDI solutions to small- and medium-sized businesses. Pursuant to the asset purchase agreement, we paid $19.4 million in cash and issued $3.4 million in common stock, or 40,478 shares, to the owners of CovalentWorks. The purchase accounting for the CovalentWorks acquisition has not been finalized as of December 31, 2018. Provisional amounts are primarily related to intangible assets. We expect to finalize the allocation of purchase price within the one-year measurement-period following the acquisition.

Purchase Price Allocation

We accounted for the acquisition as a business combination. We allocated the purchase price to the tangible and identifiable intangible assets acquired and liabilities assumed based on their estimated fair values as of the acquisition date. We engaged a third-party valuation firm to assist us in the determination of the value of the purchased intangible assets. The excess of the purchase price over the fair value of net tangible and identifiable intangible assets acquired was recorded as goodwill. Goodwill is attributed to buyer-specific value resulting from expected synergies, including long-term cost savings, which are not included in the fair values of identifiable assets.

The purchase price consisted of the following (in thousands):

Cash	$	19,431
SPS Commerce, Inc. common stock		3,371
	$	22,802

The final purchase price is subject to a net working capital adjustment to be determined by the sellers and us, pursuant to the terms of the purchase agreement.

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):

Current assets	$	244
Property and equipment		44
Goodwill		15,402
Intangible assets		7,210
Current liabilities		(56	)
Deferred revenue		(42	)
	$	22,802

Purchased Intangible Assets

The following table summarizes the estimated fair value of the purchased intangible assets and their estimated useful lives:

	Estimated		Estimated
	Fair Value		Life
Purchased Intangible Assets	(in thousands)		(in years)
Subscriber relationships	$	7,100		7
Developed technology		100		3
Trade names		10		1
Total	$	7,210

The purchased intangible assets are being amortized on a straight-line basis over their estimated useful lives. Amortization expense for the period from December 18, 2018 through December 31, 2018 was not material.

Revenue

12 Months Ended

Dec. 31, 2018

Revenue From Contract With Customer [Abstract]

Revenue

NOTE C – Revenue

We derive our revenues primarily from the following revenue streams (in thousands):

	Year Ended December 31,
	2018		2017		2016
Recurring revenues:
Fulfillment	$	190,783	$	164,682	$	139,645
Analytics		34,447		34,260		32,938
Other		5,424		4,978		4,474
Recurring Revenues		230,654		203,920		177,057
One-time revenues		17,586		16,165		16,096
	$	248,240	$	220,085	$	193,153

We determine revenue recognition through the following steps:

Identification of the contract, or contracts, with a customer

Identification of the performance obligations in the contract

Determination of the transaction price

Allocation of the transaction price to the performance obligations in the contract

Recognition of revenue when, or as, we satisfy a performance obligation

Recurring Revenues

Recurring revenues consists of recurring subscriptions from customers that utilize our Fulfillment, Analytics and Other cloud-based supply chain management solutions. Revenue for these solutions is generally recognized on a ratable basis over the contract term beginning on the date that our service is made available to the customer. Our contracts with our recurring revenue customers are recurring in nature, ranging from monthly to annual, and generally allow the customer to cancel the contract for any reason with 30 to 90 days’ notice. Timing of billings varies by customer and by contract type and are either in advance or within 30 days of the service being performed.

The deferred revenue liabilities for recurring revenue contracts are for one year or less and recognized on a ratable basis over the contract term. We have applied the optional exemption under ASC 606-10-50-14(a) and will not disclose information about the remaining performance obligations for contracts which have original durations of one year or less.

One-time Revenues

One-time revenues consist of set-up fees from customers and miscellaneous one-time fees.

Set-up fees are specific for each connection a customer has with a trading partner and many of our customers have connections with numerous trading partners. Set-up fees related to our cloud-based supply chain management solutions are nonrefundable upfront fees that are necessary for our customers to utilize our cloud-based services. These set-up fees do not provide any standalone value to our customers. Except for our Analytics solution, we have determined that the set-up fees represent a material renewal option right to our customers as they will not be incurred again upon renewal. These set-up fees and related costs are deferred and recognized ratably over two years, which is the estimated period for which a material right is present for our customers. For our Analytics solution, we have determined that the set-up fees do not represent a material customer renewal right and, as such, are deferred and recognized ratably over the estimated initial contract term, which is one year.

The table below presents the activity of the portion of the deferred revenue liability relating to set-up fees (in thousands):

	Year Ended December 31,
	2018			2017
Balances, at beginning of period	$	10,031		$	9,995
Invoiced set-up fees		10,271			10,625
Amortized set-up fees		(10,445	)		(10,589	)
Balances, at end of period	$	9,857		$	10,031

The entire balance of set-up fees will be recognized within two years and, as such, current amounts will be recognized in the next 1-12 months and long-term amounts will be recognized in the next 13-24 months.

Miscellaneous one-time fees consist of professional services and testing and certification. The deferred revenue liability for these one-time fees are for one year or less and recognized at the time service is provided. We have applied the optional exemption under ASC 606-10-50-14(a) and will not disclose information about the remaining performance obligations for contracts which have original durations of one year or less.

Deferred Costs

12 Months Ended

Dec. 31, 2018

Deferred Costs [Abstract]

Deferred Costs

NOTE D – Deferred Costs

The table below presents the activity of deferred costs and amortization of deferred costs (in thousands):

	Year Ended December 31,
	2018			2017
Balances, at beginning of period	$	39,933		$	32,117
Incurred deferred costs		49,583			44,628
Amortized deferred costs		(44,041	)		(36,812	)
Balances, at end of period	$	45,475		$	39,933

Financial Instruments

12 Months Ended

Dec. 31, 2018

Disclosure Text Block Supplement [Abstract]

Financial Instruments

NOTE E – Financial Instruments

We invest primarily in money market funds, certificates of deposit, highly liquid debt instruments of the U.S. government and U.S. corporate debt securities. All highly liquid investments with original maturities of 90 days or less are classified as cash equivalents. All investments with original maturities greater than 90 days and remaining maturities less than one year from the balance sheet date are classified as short-term investments. Investments with remaining maturities of more than one year from the balance sheet date are classified as long-term investments.

Our short- and long-term marketable securities are classified as available-for-sale. We intend to hold marketable securities until maturity; however, we may sell these securities at any time for use in current operations or for other purposes. Consequently, we may or may not keep securities with stated holding periods to maturity.

Our marketable securities are carried at fair value and unrealized gains and losses on these investments, net of taxes, are included in accumulated other comprehensive loss in the consolidated balance sheets. Realized gains or losses are included in other income (expense), net in the consolidated statements of comprehensive income. When a determination has been made that an other-than-temporary decline in fair value has occurred, the amount of the decline that is related to a credit loss is realized and is included in other income (expense), net in the consolidated statements of comprehensive income.

Cash equivalents and short- and long-term investments consisted of the following (in thousands):

	December 31,
	2018						2017
	Amortized		Unrealized		Fair		Amortized		Unrealized			Fair
	Cost		Gains (Losses)		Value		Cost		Gains (Losses)			Value
Cash equivalents:
Money market funds	$	109,265	$	—	$	109,265	$	104,544	$	—		$	104,544
Certificate of deposit		7,000		—		7,000		7,814		—			7,814
Marketable securities:
Corporate bonds		15,194		40		15,234		17,758		(57	)		17,701
Commercial paper		9,889		76		9,965		7,456		20			7,476
U.S. treasury securities		12,300		38		12,338		12,381		26			12,407
	$	153,648	$	154	$	153,802	$	149,953	$	(11	)	$	149,942
Due within one year					$	153,802						$	144,736
Due within two years						—							5,206
Total					$	153,802						$	149,942

We do not believe any of the unrealized losses represent an other-than-temporary impairment based on our assessment of available evidence as of December 31, 2018. We expect to receive the full principal and interest on all of these cash equivalents and investments.

Fair Value Measurements

We measure certain financial assets at fair value on a recurring basis based on a fair value hierarchy that requires us to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The three levels of inputs that may be used to measure fair value are:

•

Level 1 – quoted prices in active markets for identical assets or liabilities.

•

Level 2 – observable inputs other than Level 1 prices, such as (a) quoted prices for similar assets or liabilities, (b) quoted prices in markets with insufficient volume or infrequent transactions (less active markets), or (c) model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated by observable market data for substantially the full term of the assets or liabilities. We obtain the fair values of our level 2 available-for-sale securities from a professional pricing service.

•

Level 3 – unobservable inputs to the valuation methodology that are significant to the measurement of fair value of assets or liabilities.

For the earn-out liability related to the EDIAdmin acquisition, the Company utilized the Monte Carlo simulation method to estimate the fair value of this contingent liability as of the reporting date. Thousands of iterations of the simulation were performed using forecasted revenues to develop a distribution of future values of recurring revenue which, in turn, provide indicated earn-out payments. The total estimated fair value equals the sum of the average present values of the indicated earn-out payments. Changes in assumptions described above could have an impact on the payout of contingent consideration with a maximum payout being $1.7 million. The earn-out liability has been measured as Level 3 given the unobservable inputs that are significant to the measurement of the liability.

The following table presents information about our financial assets that are measured at fair value on a recurring basis and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value (in thousands):

	Level 1		Level 2		Level 3		Total
Assets at December 31, 2018:
Cash equivalents:
Money market funds	$	109,265	$	—	$	—	$	109,265
Certificate of deposit		7,000		—		—		7,000
Marketable securities:
Corporate bonds		—		15,234		—		15,234
Commercial paper		—		9,965		—		9,965
U.S. treasury securities		—		12,338		—		12,338
	$	116,265	$	37,537	$	—	$	153,802

Liabilities at December 31, 2018:
Earn-out liability	$	—	$	—	$	1,368	$	1,368
	$	—	$	—	$	1,368	$	1,368

Assets at December 31, 2017:
Cash equivalents:
Money market funds	$	104,544	$	—	$	—	$	104,544
Certificate of deposit		7,814		—		—		7,814
Marketable securities:
Corporate bonds		—		17,701		—		17,701
Commercial paper		—		7,476		—		7,476
U.S. treasury securities		—		12,407		—		12,407
	$	112,358	$	37,584	$	—	$	149,942

Allowance for Doubtful Accounts

12 Months Ended

Dec. 31, 2018

Receivables [Abstract]

Allowance for Doubtful Accounts

NOTE F – Allowance for Doubtful Accounts

The allowance for doubtful accounts activity, included in accounts receivable, net, was as follows (in thousands):

	2018			2017			2016
Balances, January 1	$	763		$	515		$	446
Provision for doubtful accounts		2,590			1,705			1,375
Write-offs, net of recoveries		(1,961	)		(1,457	)		(1,306	)
Balances, December 31	$	1,392		$	763		$	515

Property and Equipment, net

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Property and Equipment, net

NOTE G – Property and Equipment, net

Property and equipment, net included the following (in thousands):

	December 31,
	2018			2017
Computer equipment and software	$	44,781		$	35,326
Office equipment and furniture		7,985			7,439
Leasehold improvements		9,366			8,042
		62,132			50,807
Less: accumulated depreciation and amortization		(41,175	)		(33,951	)
	$	20,957		$	16,856

At December 31, 2018 and 2017, property and equipment, net included approximately $1.7 million and $2.2 million, respectively, of assets held at subsidiary and office locations outside of the U.S.

Goodwill and Intangible Assets, net

12 Months Ended

Dec. 31, 2018

Goodwill And Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets, net

NOTE H – Goodwill and Intangible Assets, net

The changes in the net carrying amount of goodwill for the years ended December 31, 2018 and 2017 are as follows (in thousands):

	2018			2017
Balances, January 1	$	51,613		$	49,777
Additions from business acquisitions		20,272			—
Foreign currency translation		(2,227	)		1,836
Balances, December 31	$	69,658		$	51,613

Intangible assets, net included the following (in thousands):

	December 31, 2018
	Carrying Amount		Accumulated Amortization			Foreign Currency Translation			Net
Subscriber relationships	$	43,212	$	(23,284	)	$	(623	)	$	19,305
Non-competition agreements		2,560		(2,247	)		(28	)		285
Technology and other		5,199		(2,012	)		(36	)		3,151
	$	50,971	$	(27,543	)	$	(687	)	$	22,741

	December 31, 2017
	Carrying Amount		Accumulated Amortization			Foreign Currency Translation		Net
Subscriber relationships	$	34,350	$	(19,592	)	$	614	$	15,372
Non-competition agreements		2,499		(2,058	)		45		486
Technology and other		2,130		(1,518	)		59		671
	$	38,979	$	(23,168	)	$	718	$	16,529

Amortization expense was $4.1 million, $4.6 million and $4.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. At December 31, 2018, future amortization expense for intangible assets was as follows (in thousands):

2019	$	5,026
2020		4,679
2021		3,845
2022		2,742
2023		2,668
Thereafter		3,781
	$	22,741

Other Assets

12 Months Ended

Dec. 31, 2018

Other Assets [Abstract]

Other Assets

NOTE I – Other Assets

The changes in the net amount of capitalized implementation costs for internal-use software from hosting arrangements for the years ended December 31, 2018 and 2017 are as follows (in thousands):

	2018		2017
Balances, January 1	$	—	$	—
Capitalized implementation fees		455		—
Amortization of implementation fees		—		—
Balances, December 31	$	455	$	—

There were no impairment losses in relation to the capitalized implementation costs for the periods presented.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE J – Commitments and Contingencies

Operating Leases

We are obligated under non-cancellable operating leases primarily for office space. Rent expense for all operating leases, which includes minimum lease payments and other charges such as common area maintenance fees, charged to operations was $5.6 million, $4.9 million and $5.0 million for the years ended December 31, 2018, 2017 and 2016, respectively.

On December 20, 2017, we executed the fourth amendment to our lease agreement for our current headquarters located in Minneapolis, Minnesota where we lease approximately 189,000 square feet under an agreement that expires on April 30, 2025. We have agreed to expand our headquarters premises by approximately 25,000 square feet during 2020. Our lease agreement also includes a further expansion right and a right of first offer to lease certain additional space and two options to extend the term of the lease for five years at a market rate determined in accordance with the lease. We received $3.2 million in incentives upon execution of the amendment and we are owed an additional $2.1 million in incentives upon expansion of our square footage in 2018, both of which have been incorporated into our deferred rent calculation.

At December 31, 2018, our future minimum payments under operating leases were as follows (in thousands):

2019	$	4,209
2020		3,542
2021		4,414
2022		4,042
2023		3,854
Thereafter		4,817
	$	24,878

Other Contingencies

We may be involved in various claims and legal actions in the normal course of business. Our management believes that the outcome of any such claims and legal actions will not have a material effect on our financial position, results of operations or cash flows.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Stockholders’ Equity

NOTE K – Stockholders’ Equity

Common Stock Issued

In connection with the acquisition of CovalentWorks (see Note B), we issued 40,478 shares of SPS common stock as calculated according to the terms of the purchase agreement. The fair value of the shares we issued of approximately $3.4 million was determined using the closing price of our common stock on December 18, 2018, the closing date of the transaction.

Stock Repurchase Program

On November 2, 2017, our board of directors authorized a program to repurchase up to $50.0 million of common stock. Under the program, purchases may be made from time to time in the open market over two years. The number of shares to be purchased and the timing of purchases will be based on the price of our common stock, general business and market conditions and other investment considerations and factors.

The program does not obligate us to repurchase any specific number of shares and may be suspended or discontinued at any time without prior notice. We intend to finance the share repurchase program with cash on hand.

We repurchased 289,745 shares at a cost of $19.9 million and 122,147 shares at a cost of $5.8 million for the years ended December 31, 2018 and December 31, 2017, respectively. Of the $50.0 million share repurchases authorized, $24.3 million was available for future share repurchases at December 31, 2018.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

NOTE L – Stock-Based Compensation

Our equity compensation plans provide for the grant of incentive and nonqualified stock options, as well as other stock-based awards including restricted stock and restricted stock units, to employees, non-employee directors and other consultants who provide services to us. Restricted stock awards result in the issuance of new shares when granted. For other stock-based awards, new shares are issued when the award is exercised, vested or released according to the terms of the agreement. In January 2018 and February 2017, 1,027,620 and 1,024,868 additional shares, respectively, were reserved for future issuance under our 2010 Equity Incentive Plan. At December 31, 2018, there were approximately 5.3 million shares available for grant under approved equity compensation plans.

We recorded stock-based compensation expense of $12.5 million, $12.7 million and $8.0 million for the years ended December 31, 2018, 2017 and 2016, respectively. During the year ended December 31, 2017, stock-based compensation expense included a one-time $3.6 million charge due to a modification to our Chief Executive Officer’s employment agreement which resulted in immediate vesting, and expensing, of his outstanding stock-based compensation awards based on his retirement eligibility. Stock-based compensation expense was allocated as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Cost of revenues	$	2,168	$	1,887	$	1,309
Operating expenses
Sales and marketing		2,675		2,197		2,412
Research and development		1,505		949		618
General and administrative		6,162		7,694		3,684
Total stock-based compensation expense	$	12,510	$	12,727	$	8,023

Stock-based compensation expense by type was as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Stock Options	$	3,355	$	5,223	$	3,777
Performance Share Units		1,034		—		—
Restricted Stock Units		5,930		6,526		3,386
Restricted Stock Awards		487		318		308
Employee Stock Purchase Plan		466		660		552
401K Stock Match		1,238		—		—
Total stock-based compensation expense	$	12,510	$	12,727	$	8,023

As of December 31, 2018, there was approximately $13.6 million of unrecognized stock-based compensation expense under our equity compensation plans, which is expected to be recognized on a straight-line basis over a weighted-average period of 2.3 years.

Stock Options

Stock options generally vest over four years and have a contractual term of seven to ten years from the date of grant. Our stock option activity was as follows:

				Weighted Average
	Options			Exercise Price
	(#)			($/share)
Outstanding at December 31, 2015		943,103		$	37.91
Granted		340,609			48.58
Exercised		(221,630	)		19.42
Forfeited		(46,070	)		55.58
Outstanding at December 31, 2016		1,016,012			44.72
Granted		172,697			55.87
Exercised		(65,502	)		21.53
Forfeited		(25,876	)		55.93
Outstanding at December 31, 2017		1,097,331			47.60
Granted		181,472			59.88
Exercised		(344,334	)		41.66
Forfeited		(61,235	)		56.67
Outstanding at December 31, 2018		873,234			51.86

Of the total outstanding options at December 31, 2018, 576,842 were exercisable with a weighted average exercise price of $50.10 per share. The total outstanding options had a weighted average remaining contractual life of 4.0 years.

The fair value of options that vested during the years ended December 31, 2018, 2017 and 2016 was $3.7 million, $4.2 million and $3.4 million, respectively.

The intrinsic value of options exercised during the years ended December 31, 2018, 2017 and 2016 was $14.9 million, $2.8 million and $8.6 million, respectively. The intrinsic value of outstanding options at December 31, 2018, 2017 and 2016 was $26.7 million, $7.3 million and $25.6 million, respectively.

The weighted-average fair values per share of options granted during the years ended December 31, 2018, 2017 and 2016 were $19.48, $18.85 and $16.13, respectively. The fair values of the options granted were estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2018			2017			2016
Volatility		35	%		38	%		38	%
Dividend yield		—			—			—
Life (in years)		4.44			4.51			4.54
Risk-free interest rate		2.54	%		1.85	%		1.19	%

The expected volatility of the options is based on the historical volatility of our common stock. We have not issued dividends on our common stock and do not expect to do so in the foreseeable future. The expected term of the options is based on the simplified method which does not consider historical employee exercise behavior. The risk-free interest rate is based on the U.S. Treasury rates at the date of grant with maturity dates approximately equal to the expected life at the grant date.

Performance Share Units and Restricted Stock Units and Awards

In February 2018, our executive officers were granted performance share unit (“PSU”) awards with vesting contingent on the Company’s total shareholder return as compared to indexed total shareholder return over the course of a three-year performance period (fiscal years 2018 – 2020). The grant date fair value was estimated using a Monte Carlo simulation that utilizes multiple input variables that determine the probability of satisfying the performance conditions stipulated in the award and calculates the fair market value for the performance stock units granted. Expense is recognized on a straight-line basis over the vesting period, regardless of whether the market condition is satisfied as the likelihood of the market condition being met is included in the fair-value measurement of the award.

In February 2017, our executive officers were granted PSU awards with vesting contingent on successful attainment of pre-determined revenue targets over the course of a three-year performance period (fiscal 2017 – 2019). The fair value is measured as the number of performance shares expected to be earned multiplied by the grant date fair value of our shares. The number of performance shares expected to vest during the current service period is estimated and the fair value of those shares is recognized over the remaining service period less any amounts already recognized.

Restricted stock units (“RSU”) vest over four years and, upon vesting, the holder is entitled to receive shares of our common stock. With restricted stock awards (“RSA”), shares of our common stock are issued when the award is granted and the restrictions lapse over one year.

Our PSU and RSU activity was as follows:

				Weighted Average
	PSUs and RSUs			Grant Date Fair
	(#)			Value ($/share)
Outstanding at December 31, 2015		140,565		$	56.88
Granted		115,896			48.32
Vested and common stock issued		(52,133	)		48.19
Forfeited		(15,286	)		55.48
Outstanding at December 31, 2016		189,042			54.14
Granted		211,168			55.62
Vested and common stock issued		(64,950	)		53.64
Forfeited		(13,348	)		55.39
Outstanding at December 31, 2017		321,912			55.16
Granted		172,795			66.03
Vested and common stock issued		(81,561	)		56.32
Forfeited		(35,811	)		55.04
Outstanding at December 31, 2018		377,335			59.90

The number of PSUs and RSUs outstanding at December 31, 2018 included 54,688 units that have vested, but the shares of common stock have not yet been issued pursuant to the terms of the agreement.

Our RSA activity was as follows:

				Weighted Average
	RSAs			Grant Date Fair
	(#)			Value ($/share)
Outstanding at December 31, 2015		1,032		$	67.39
Restricted common stock issued		6,078			52.27
Restrictions lapsed		(5,586	)		55.06
Outstanding at December 31, 2016		1,524			52.28
Restricted common stock issued		5,454			58.29
Restrictions lapsed		(5,610	)		56.65
Outstanding at December 31, 2017		1,368			58.29
Restricted common stock issued		7,304			74.43
Restrictions lapsed		(6,840	)		71.20
Outstanding at December 31, 2018		1,832			74.44

Employee Stock Purchase Plan

We have an employee stock purchase plan which allows participating employees to purchase shares of our common stock at a discount through payroll deductions. The plan is available to all employees subject to certain eligibility requirements. Participating employees may purchase common stock, on a voluntary after tax basis, at a price that is the lower of 85% of the fair market value of one share of common stock at the beginning or end of each stock purchase period. The plan consists of two six-month offering periods, beginning on January 1 and July 1 of each calendar year. A total of 1.0 million shares of common stock are remaining for issuance under the plan.

For the offering periods in the years ended December 31, 2018, 2017 and 2016, we withheld approximately $1.7 million, $1.9 million and $1.7 million, respectively, from employees participating in the plan and purchased 34,798 shares, 40,968 shares and 33,357 shares, respectively, on their behalf.

For the years ended December 31, 2018, 2017 and 2016, we recorded approximately $0.5 million, $0.7 million and $0.6 million, respectively, of stock-based compensation expense associated with the employee stock purchase plan. The fair value was estimated based on the market price of our common stock at the beginning of each offering period and using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2018			2017			2016
Volatility		26	%		32	%		37	%
Dividend yield		—			—			—
Life (in years)		0.50			0.50			0.50
Risk-free interest rate		1.77	%		0.90	%		0.42	%

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

NOTE M – Income Taxes

Our provisions for income taxes included current federal, foreign and state income tax expense, as well as deferred tax expense as follows (in thousands):

	Year Ended December 31,
	2018			2017			2016
Current
Federal	$	—		$	(184	)	$	3,684
State		1,103			258			555
Foreign		540			652			599
Deferred
Federal		3,011			10,262			(1,337	)
State		224			(291	)		(169	)
Foreign		(410	)		(355	)		(577	)
	$	4,468		$	10,342		$	2,755

The tax provision for the year ended December 31, 2017 includes a $0.4 million reclass of alternative minimum tax (“AMT”) credit carryforwards from the deferred federal provision to current federal provision. These unutilized AMT credit carryforwards become partially refundable in 2019, 2020 and 2021 and fully refundable in 2022.

A reconciliation of the expected federal income tax at the statutory rate to the provision for income taxes was as follows (in thousands):

	Year Ended December 31,
	2018			2017			2016
Expected federal income tax at statutory rate	$	5,951		$	3,635		$	2,662
State income taxes, net of federal tax effect		1,293			417			284
Tax impact of foreign activity		57			(105	)		(115	)
Nondeductible executive compensation		902			530			159
Nondeductible expenses		351			268			213
Change in valuation allowance		(4	)		16			(35	)
Change in state deferred rate		38			(134	)		(67	)
Research and development credit		(1,843	)		(227	)		(261	)
Tax impact of Tax Cuts and Jobs Act		—			6,796			—
Tax impact of stock activity		(2,438	)		(925	)		—
Other		161			71			(85	)
Total provision for income taxes	$	4,468		$	10,342		$	2,755

The Tax Act, which was enacted on December 22, 2017, reduced the corporate federal income tax rate to 21.0% effective January 1, 2018, resulting in discrete tax expense of $6.8 million for the reduction of deferred tax assets. Also, the Tax Act expanded the deduction limits on executive compensation and included transition rules for previously awarded compensation.

Differences between our effective tax rate and statutory tax rates are primarily due to the federal research and development credit partially offset by permanently non-deductible expense. Additionally, under ASU 2016-09, excess tax benefits generated upon settlement or exercise of stock awards are now recognized as a reduction to income tax expense as a discrete tax item in the period that the event occurs creating potentially significant fluctuation in tax expense by year.

The significant components of our deferred tax assets (liabilities) were as follows (in thousands):

	December 31,
	2018						2017
Deferred tax assets
Net operating loss and credit carryforwards	$	8,356					$	11,067
Stock-based compensation expense		3,647						4,273
Accounts receivable allowances		464						307
Accrued expenses		3,185						2,126
Other		180						182
Gross deferred tax asset					15,832						17,955
Less: valuation allowance		(797	)					(602	)
Total net deferred tax asset					15,035						17,353
Deferred tax liability
Deferred operations		(2,787	)					(3,850	)
Foreign operations		(135	)					(133	)
Depreciation and amortization		(2,943	)					(1,536	)
Other		(90	)					(24	)
Total deferred tax liability					(5,955	)					(5,543	)
Net deferred tax assets				$	9,080					$	11,810

As of December 31, 2018, we had net operating loss carryforwards of $37.5 million for U.S. federal tax purposes. We also had $4.1 million of various state net operating loss carryforwards. The loss carryforwards for federal tax purposes will expire between 2020 and 2038 if not utilized. The loss carryforwards for state tax purposes will expire between 2019 and 2031 if not utilized.

Section 382 of the U.S. Internal Revenue Code generally imposes an annual limitation on the amount of net operating loss carryforwards that might be used to offset taxable income when a corporation has undergone significant changes in stock ownership. We have performed a Section 382 analysis and we believe that approximately $17.6 million of federal losses will expire unused due to Section 382 limitations. The maximum annual limitation of federal net operating losses under Section 382 is approximately $1.0 million. This limitation could be further restricted if any ownership changes occur in future years. Accordingly, our deferred tax assets are reported net of the Section 382 limitations.

As of December 31, 2018 we had federal research and development credit carryforwards, net of Section 383 limitations, of $3.0 million, which, if not utilized, will begin to expire in 2030. We had state research and development credit carryforwards of $1.0 million which, if not utilized, will begin to expire in 2025.

As of December 31, 2018, we had a valuation allowance against our deferred tax assets of $0.8 million. The valuation allowance is established for state credit carryforwards that we do not expect to utilize based on our current expectations of future state taxable income.

We are subject to income taxes for U.S. federal and various state and international jurisdictions. We are generally subject to U.S. federal and state tax examinations for all prior tax years due to our net operating loss carryforwards and the utilization of the carryforwards in years still open under statute.

As of December 31, 2018, we do not have any unrecognized tax benefits. It is our practice to recognize interest and penalties accrued on any unrecognized tax benefits as a component of income tax expense. We do not expect any material changes in our unrecognized tax positions over the next 12 months.

Net Income Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Net Income Per Share

NOTE N – Net Income Per Share

The following table presents the components of the computation of basic and diluted net income per share for the periods indicated (in thousands, except per share amounts):

	Year Ended December 31,
	2018		2017		2016
Numerator
Net income	$	23,872	$	351	$	4,963
Denominator
Weighted average common shares outstanding, basic		17,196		17,183		16,947
Options to purchase common stock		306		150		267
Restricted stock units		104		23		27
Weighted average common shares outstanding, diluted		17,606		17,356		17,241
Net income per share
Basic	$	1.39	$	0.02	$	0.29
Diluted	$	1.36	$	0.02	$	0.29

For the year ended December 31, 2018, 2017 and 2016, the effect of less than 1,000, approximately 283,000 and approximately 5,000 outstanding potential common shares, respectively, were excluded from the calculation of diluted net income per share as they were anti-dilutive.

Retirement Savings Plan

12 Months Ended

Dec. 31, 2018

Compensation And Retirement Disclosure [Abstract]

Retirement Savings Plan

NOTE O – Retirement Savings Plan

We sponsor a 401(k) retirement savings plan for our employees. Employees can contribute up to 100% of their compensation, subject to the limits established by law. In 2018, we increased our match to 50% of the employee’s contribution up to the first 6% of pre-tax annual compensation. A portion of our match is in company stock, which is purchased from the open market by our plan provider and immediately deposited into the employee’s 401(k) account, which resulted in $1.2 million of stock-based compensation expense in 2018. Additionally, we make statutory contributions to retirement plans as required by local foreign government regulations. Our total contributions to the plan were $2.9 million, $1.6 million and $1.4 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Related Party Transactions

12 Months Ended

Dec. 31, 2018

Related Party Transactions

NOTE P – Related Party Transactions

SPS Commerce Foundation (the “Foundation”) is a Minnesota non-profit organization exempt from federal taxation under Section 501(c)(3) of the Internal Revenue Code. The Foundation was formed in 2015 to engage in, advance, support, promote and administer charitable activities. The directors of the Foundation are also our officers. These officers receive no compensation from the Foundation for the management services performed for the Foundation. The Foundation is not a subsidiary of ours and the financial results of the Foundation are not consolidated with our financial statements. We made contributions of $0.7 million and $0.2 million to the Foundation for the years ended December 31, 2018 and 2017, respectively. We have no current legal obligations for future commitments to the Foundation.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (Unaudited)

NOTE Q – Selected Quarterly Financial Data (Unaudited)

The following table presents our selected unaudited quarterly statements of comprehensive income data (in thousands, except per share amounts):

	For the Three Months Ended
2018	Mar 31		Jun 30		Sep 30		Dec 31
Revenues	$	59,092	$	61,091	$	62,868	$	65,189
Gross profit		39,334		40,689		42,457		44,012
Income from operations		4,300		5,965		8,257		8,209
Net income		3,254		5,416		8,061		7,141
Diluted earnings per share	$	0.19	$	0.31	$	0.45	$	0.40

	For the Three Months Ended
2017	Mar 31		Jun 30		Sep 30		Dec 31
Revenues	$	51,879	$	54,092	$	56,057	$	58,057
Gross profit		34,549		35,901		37,412		38,598
Income from operations		3,379		2,956		3,354		292
Net income (loss)		2,985		1,968		2,176		(6,778	)
Diluted earnings per share	$	0.17	$	0.11	$	0.13	$	(0.39	)

General (Policies)

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Business Description

Basis of Presentation

Foreign Currency Translation

Use of Estimates

Business Combinations

Segment Information

We operate in and report on one segment, which is supply chain management solutions.

Risk and Uncertainties

Concentration of Credit Risk

Cash and Cash Equivalents

Cash and cash equivalents consist of cash and highly liquid investments with original maturities of less than 90 days. Cash and cash equivalents are stated at fair value.

Investments

Fair Value of Financial Instruments

Accounts Receivable

Property and Equipment

Computer equipment and software: 2 to 3 years

Office equipment and furniture: 5 to 7 years

Leasehold improvements: the shorter of the useful life of the asset or the remaining term of the lease

Research and Development

Research and development costs primarily include maintenance and data conversion activities related to our cloud-based supply chain management solutions and are expensed as incurred.

Goodwill

Intangible Assets

Internal-use Software Implementation Assets

Impairment of Long-Lived Assets

Revenue Recognition

We determine revenue recognition through the following steps:

Identification of the contract, or contracts, with a customer

Identification of the performance obligations in the contract

Determination of the transaction price

Allocation of the transaction price to the performance obligations in the contract

Recognition of revenue when, or as, we satisfy a performance obligation

See Note C for further descriptions of our revenue recognition policy.

Deferred Costs

Stock-Based Compensation

Income Taxes

Net Income (Loss) Per Share

Net Income Per Share

Recently Adopted Accounting Pronouncements

Selected audited consolidated balance sheet line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	December 31, 2017
	As previously
	reported			Adjustments			As adjusted
ASSETS
Deferred costs	$	25,091		$	4,875		$	29,966
Deferred costs, non-current		6,770			3,197			9,967
Deferred income tax asset		17,551			(3,854	)		13,697
LIABILITIES
Accrued compensation		15,886			(658	)		15,228
Deferred revenue		16,407			1,456			17,863
Deferred revenue, non-current		10,602			(7,871	)		2,731
STOCKHOLDERS’ EQUITY
Accumulated deficit		(19,902	)		11,291			(8,611	)

Selected audited consolidated statement of operations line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported		Adjustments			As adjusted
Revenues	$	193,295	$	(142	)	$	193,153
Operating expenses
Sales and marketing		65,886		990			66,876
Income from operations		7,517		(1,132	)		6,385
Income tax expense		3,140		(385	)		2,755
Net income	$	5,710	$	(747	)	$	4,963
Net income per share
Basic	$	0.34		(0.05	)	$	0.29
Diluted	$	0.33		(0.04	)	$	0.29

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Revenues	$	220,566		$	(481	)	$	220,085
Operating expenses
Sales and marketing		73,295			(2,034	)		71,261
Income from operations		8,428			1,553			9,981
Income tax expense		11,580			(1,238	)		10,342
Net income (loss)	$	(2,440	)	$	2,791		$	351
Net income (loss) per share
Basic	$	(0.14	)		0.16		$	0.02
Diluted	$	(0.14	)		0.16		$	0.02

Selected audited consolidated statement of cash flows line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income	$	5,710		$	(747	)	$	4,963
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		(1,698	)		(385	)		(2,083	)
Changes in assets and liabilities
Deferred costs		(4,964	)		879			(4,085	)
Accrued compensation		2,180			111			2,291
Deferred revenue		2,710			142			2,852
Net cash provided by operating activities		18,765			—			18,765

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income (loss)	$	(2,440	)	$	2,791		$	351
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		10,854			(1,238	)		9,616
Changes in assets and liabilities
Deferred costs		(6,548	)		(1,265	)		(7,813	)
Accrued compensation		2,073			(769	)		1,304
Deferred revenue		5,107			481			5,588
Net cash provided by operating activities		31,050			—			31,050

We early adopted ASU 2018-15 as of October 1, 2018, under the prospective method. Additional disclosure regarding capitalized implementation costs is included within Note I.

Accounting Pronouncements Not Yet Adopted

General (Tables)

12 Months Ended

Dec. 31, 2018

ASU 2014-09 [Member]

Adoption of Accounting Standard Changes on Financial Statements

Selected audited consolidated balance sheet line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	December 31, 2017
	As previously
	reported			Adjustments			As adjusted
ASSETS
Deferred costs	$	25,091		$	4,875		$	29,966
Deferred costs, non-current		6,770			3,197			9,967
Deferred income tax asset		17,551			(3,854	)		13,697
LIABILITIES
Accrued compensation		15,886			(658	)		15,228
Deferred revenue		16,407			1,456			17,863
Deferred revenue, non-current		10,602			(7,871	)		2,731
STOCKHOLDERS’ EQUITY
Accumulated deficit		(19,902	)		11,291			(8,611	)

Selected audited consolidated statement of operations line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported		Adjustments			As adjusted
Revenues	$	193,295	$	(142	)	$	193,153
Operating expenses
Sales and marketing		65,886		990			66,876
Income from operations		7,517		(1,132	)		6,385
Income tax expense		3,140		(385	)		2,755
Net income	$	5,710	$	(747	)	$	4,963
Net income per share
Basic	$	0.34		(0.05	)	$	0.29
Diluted	$	0.33		(0.04	)	$	0.29

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Revenues	$	220,566		$	(481	)	$	220,085
Operating expenses
Sales and marketing		73,295			(2,034	)		71,261
Income from operations		8,428			1,553			9,981
Income tax expense		11,580			(1,238	)		10,342
Net income (loss)	$	(2,440	)	$	2,791		$	351
Net income (loss) per share
Basic	$	(0.14	)		0.16		$	0.02
Diluted	$	(0.14	)		0.16		$	0.02

Selected audited consolidated statement of cash flows line items, which reflect the adoption of ASU 2014-09 are as follows (in thousands):

	For the twelve months ended December 31, 2016
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income	$	5,710		$	(747	)	$	4,963
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		(1,698	)		(385	)		(2,083	)
Changes in assets and liabilities
Deferred costs		(4,964	)		879			(4,085	)
Accrued compensation		2,180			111			2,291
Deferred revenue		2,710			142			2,852
Net cash provided by operating activities		18,765			—			18,765

	For the twelve months ended December 31, 2017
	As previously
	reported			Adjustments			As adjusted
Cash flows from operating activities
Net income (loss)	$	(2,440	)	$	2,791		$	351
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes		10,854			(1,238	)		9,616
Changes in assets and liabilities
Deferred costs		(6,548	)		(1,265	)		(7,813	)
Accrued compensation		2,073			(769	)		1,304
Deferred revenue		5,107			481			5,588
Net cash provided by operating activities		31,050			—			31,050

Business Acquisitions (Tables)

12 Months Ended

Dec. 31, 2018

E D I Admin [Member]

Business Acquisition [Line Items]

Business Purchase Price

The purchase price consisted of the following (in thousands):

Cash	$	7,461
Fair value of earn-out liability		1,274
	$	8,735

Estimated Fair Values of Assets Acquired and Liabilities Assumed at Acquisition Date

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):

Current assets	$	631
Goodwill		4,871
Intangible assets		3,400
Current liabilities		(57	)
Deferred revenue		(110	)
	$	8,735

Estimated Fair Value of Purchased Intangible Assets and Estimated Useful Lives

The following table summarizes the estimated fair value of the purchased intangible assets and their estimated useful lives:

	Estimated		Estimated
	Fair Value		Life
Purchased Intangible Assets	(in thousands)		(in years)
Subscriber relationships	$	600		10
Developed technology		2,800		10
Total	$	3,400

CovalentWorks [Member]

Business Acquisition [Line Items]

Business Purchase Price

The purchase price consisted of the following (in thousands):

Cash	$	19,431
SPS Commerce, Inc. common stock		3,371
	$	22,802

Estimated Fair Values of Assets Acquired and Liabilities Assumed at Acquisition Date

The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date (in thousands):

Current assets	$	244
Property and equipment		44
Goodwill		15,402
Intangible assets		7,210
Current liabilities		(56	)
Deferred revenue		(42	)
	$	22,802

Estimated Fair Value of Purchased Intangible Assets and Estimated Useful Lives

The following table summarizes the estimated fair value of the purchased intangible assets and their estimated useful lives:

	Estimated		Estimated
	Fair Value		Life
Purchased Intangible Assets	(in thousands)		(in years)
Subscriber relationships	$	7,100		7
Developed technology		100		3
Trade names		10		1
Total	$	7,210

Revenue (Tables)

12 Months Ended

Dec. 31, 2018

Revenue From Contract With Customer [Abstract]

Summary of Revenues by Revenue Stream

We derive our revenues primarily from the following revenue streams (in thousands):

	Year Ended December 31,
	2018		2017		2016
Recurring revenues:
Fulfillment	$	190,783	$	164,682	$	139,645
Analytics		34,447		34,260		32,938
Other		5,424		4,978		4,474
Recurring Revenues		230,654		203,920		177,057
One-time revenues		17,586		16,165		16,096
	$	248,240	$	220,085	$	193,153

Summary of Deferred Revenue Liability Relating to Set-Up Fees

The table below presents the activity of the portion of the deferred revenue liability relating to set-up fees (in thousands):

	Year Ended December 31,
	2018			2017
Balances, at beginning of period	$	10,031		$	9,995
Invoiced set-up fees		10,271			10,625
Amortized set-up fees		(10,445	)		(10,589	)
Balances, at end of period	$	9,857		$	10,031

Deferred Costs (Tables)

12 Months Ended

Dec. 31, 2018

Deferred Costs [Abstract]

Summary of Deferred Costs and Amortization of Deferred Costs

The table below presents the activity of deferred costs and amortization of deferred costs (in thousands):

	Year Ended December 31,
	2018			2017
Balances, at beginning of period	$	39,933		$	32,117
Incurred deferred costs		49,583			44,628
Amortized deferred costs		(44,041	)		(36,812	)
Balances, at end of period	$	45,475		$	39,933

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Financial Instruments Owned At Fair Value [Abstract]

Summary of Cash Equivalents and Short and Long-term Investments

Cash equivalents and short- and long-term investments consisted of the following (in thousands):

	December 31,
	2018						2017
	Amortized		Unrealized		Fair		Amortized		Unrealized			Fair
	Cost		Gains (Losses)		Value		Cost		Gains (Losses)			Value
Cash equivalents:
Money market funds	$	109,265	$	—	$	109,265	$	104,544	$	—		$	104,544
Certificate of deposit		7,000		—		7,000		7,814		—			7,814
Marketable securities:
Corporate bonds		15,194		40		15,234		17,758		(57	)		17,701
Commercial paper		9,889		76		9,965		7,456		20			7,476
U.S. treasury securities		12,300		38		12,338		12,381		26			12,407
	$	153,648	$	154	$	153,802	$	149,953	$	(11	)	$	149,942
Due within one year					$	153,802						$	144,736
Due within two years						—							5,206
Total					$	153,802						$	149,942

Summary of Financial Assets Measured at Fair Value on a Recurring Basis

	Level 1		Level 2		Level 3		Total
Assets at December 31, 2018:
Cash equivalents:
Money market funds	$	109,265	$	—	$	—	$	109,265
Certificate of deposit		7,000		—		—		7,000
Marketable securities:
Corporate bonds		—		15,234		—		15,234
Commercial paper		—		9,965		—		9,965
U.S. treasury securities		—		12,338		—		12,338
	$	116,265	$	37,537	$	—	$	153,802

Liabilities at December 31, 2018:
Earn-out liability	$	—	$	—	$	1,368	$	1,368
	$	—	$	—	$	1,368	$	1,368

Assets at December 31, 2017:
Cash equivalents:
Money market funds	$	104,544	$	—	$	—	$	104,544
Certificate of deposit		7,814		—		—		7,814
Marketable securities:
Corporate bonds		—		17,701		—		17,701
Commercial paper		—		7,476		—		7,476
U.S. treasury securities		—		12,407		—		12,407
	$	112,358	$	37,584	$	—	$	149,942

Allowance for Doubtful Accounts (Tables)

12 Months Ended

Dec. 31, 2018

Receivables [Abstract]

Schedule of Allowance for Doubtful Activity Included in Accounts Receivable Net

The allowance for doubtful accounts activity, included in accounts receivable, net, was as follows (in thousands):

	2018			2017			2016
Balances, January 1	$	763		$	515		$	446
Provision for doubtful accounts		2,590			1,705			1,375
Write-offs, net of recoveries		(1,961	)		(1,457	)		(1,306	)
Balances, December 31	$	1,392		$	763		$	515

Property and Equipment, net (Tables)

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net included the following (in thousands):

	December 31,
	2018			2017
Computer equipment and software	$	44,781		$	35,326
Office equipment and furniture		7,985			7,439
Leasehold improvements		9,366			8,042
		62,132			50,807
Less: accumulated depreciation and amortization		(41,175	)		(33,951	)
	$	20,957		$	16,856

Goodwill and Intangible Assets, net (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill And Intangible Assets Disclosure [Abstract]

Schedule of Changes in Net Carrying Amount of Goodwill

The changes in the net carrying amount of goodwill for the years ended December 31, 2018 and 2017 are as follows (in thousands):

	2018			2017
Balances, January 1	$	51,613		$	49,777
Additions from business acquisitions		20,272			—
Foreign currency translation		(2,227	)		1,836
Balances, December 31	$	69,658		$	51,613

Intangible Assets

Intangible assets, net included the following (in thousands):

	December 31, 2018
	Carrying Amount		Accumulated Amortization			Foreign Currency Translation			Net
Subscriber relationships	$	43,212	$	(23,284	)	$	(623	)	$	19,305
Non-competition agreements		2,560		(2,247	)		(28	)		285
Technology and other		5,199		(2,012	)		(36	)		3,151
	$	50,971	$	(27,543	)	$	(687	)	$	22,741

	December 31, 2017
	Carrying Amount		Accumulated Amortization			Foreign Currency Translation		Net
Subscriber relationships	$	34,350	$	(19,592	)	$	614	$	15,372
Non-competition agreements		2,499		(2,058	)		45		486
Technology and other		2,130		(1,518	)		59		671
	$	38,979	$	(23,168	)	$	718	$	16,529

Future Amortization Expense for Intangible Assets

At December 31, 2018, future amortization expense for intangible assets was as follows (in thousands):

2019	$	5,026
2020		4,679
2021		3,845
2022		2,742
2023		2,668
Thereafter		3,781
	$	22,741

Other Assets (Tables)

12 Months Ended

Dec. 31, 2018

Other Assets [Abstract]

Summary of Changes in Net Amount of Capitalized Implementation Costs for Internal-use Software from Hosting Arrangements

The changes in the net amount of capitalized implementation costs for internal-use software from hosting arrangements for the years ended December 31, 2018 and 2017 are as follows (in thousands):

	2018		2017
Balances, January 1	$	—	$	—
Capitalized implementation fees		455		—
Amortization of implementation fees		—		—
Balances, December 31	$	455	$	—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Future Minimum Payments Under Operating Leases

At December 31, 2018, our future minimum payments under operating leases were as follows (in thousands):

2019	$	4,209
2020		3,542
2021		4,414
2022		4,042
2023		3,854
Thereafter		4,817
	$	24,878

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Stock-Based Compensation Expense

Stock-based compensation expense was allocated as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Cost of revenues	$	2,168	$	1,887	$	1,309
Operating expenses
Sales and marketing		2,675		2,197		2,412
Research and development		1,505		949		618
General and administrative		6,162		7,694		3,684
Total stock-based compensation expense	$	12,510	$	12,727	$	8,023

Stock-based compensation expense by type was as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Stock Options	$	3,355	$	5,223	$	3,777
Performance Share Units		1,034		—		—
Restricted Stock Units		5,930		6,526		3,386
Restricted Stock Awards		487		318		308
Employee Stock Purchase Plan		466		660		552
401K Stock Match		1,238		—		—
Total stock-based compensation expense	$	12,510	$	12,727	$	8,023

Stock Option Activity

Our stock option activity was as follows:

				Weighted Average
	Options			Exercise Price
	(#)			($/share)
Outstanding at December 31, 2015		943,103		$	37.91
Granted		340,609			48.58
Exercised		(221,630	)		19.42
Forfeited		(46,070	)		55.58
Outstanding at December 31, 2016		1,016,012			44.72
Granted		172,697			55.87
Exercised		(65,502	)		21.53
Forfeited		(25,876	)		55.93
Outstanding at December 31, 2017		1,097,331			47.60
Granted		181,472			59.88
Exercised		(344,334	)		41.66
Forfeited		(61,235	)		56.67
Outstanding at December 31, 2018		873,234			51.86

Weighted Average Fair Value Per Share of Options Granted, Assumptions

	Year Ended December 31,
	2018			2017			2016
Volatility		35	%		38	%		38	%
Dividend yield		—			—			—
Life (in years)		4.44			4.51			4.54
Risk-free interest rate		2.54	%		1.85	%		1.19	%

Fair Value Estimation of Common Stock Using Black-Scholes Option Pricing Model, Weighted-Average Assumptions

The fair value was estimated based on the market price of our common stock at the beginning of each offering period and using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Year Ended December 31,
	2018			2017			2016
Volatility		26	%		32	%		37	%
Dividend yield		—			—			—
Life (in years)		0.50			0.50			0.50
Risk-free interest rate		1.77	%		0.90	%		0.42	%

Performance Share Units and Restricted Stock Units [Member]

Performance Share Units and Restricted Stock Units and Restricted Stock Awards

Our PSU and RSU activity was as follows:

				Weighted Average
	PSUs and RSUs			Grant Date Fair
	(#)			Value ($/share)
Outstanding at December 31, 2015		140,565		$	56.88
Granted		115,896			48.32
Vested and common stock issued		(52,133	)		48.19
Forfeited		(15,286	)		55.48
Outstanding at December 31, 2016		189,042			54.14
Granted		211,168			55.62
Vested and common stock issued		(64,950	)		53.64
Forfeited		(13,348	)		55.39
Outstanding at December 31, 2017		321,912			55.16
Granted		172,795			66.03
Vested and common stock issued		(81,561	)		56.32
Forfeited		(35,811	)		55.04
Outstanding at December 31, 2018		377,335			59.90

Restricted Stock Award [Member]

Performance Share Units and Restricted Stock Units and Restricted Stock Awards

Our RSA activity was as follows:

				Weighted Average
	RSAs			Grant Date Fair
	(#)			Value ($/share)
Outstanding at December 31, 2015		1,032		$	67.39
Restricted common stock issued		6,078			52.27
Restrictions lapsed		(5,586	)		55.06
Outstanding at December 31, 2016		1,524			52.28
Restricted common stock issued		5,454			58.29
Restrictions lapsed		(5,610	)		56.65
Outstanding at December 31, 2017		1,368			58.29
Restricted common stock issued		7,304			74.43
Restrictions lapsed		(6,840	)		71.20
Outstanding at December 31, 2018		1,832			74.44

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Provision for Income Taxes

Our provisions for income taxes included current federal, foreign and state income tax expense, as well as deferred tax expense as follows (in thousands):

	Year Ended December 31,
	2018			2017			2016
Current
Federal	$	—		$	(184	)	$	3,684
State		1,103			258			555
Foreign		540			652			599
Deferred
Federal		3,011			10,262			(1,337	)
State		224			(291	)		(169	)
Foreign		(410	)		(355	)		(577	)
	$	4,468		$	10,342		$	2,755

Reconciliation of the Provision for Income Taxes to the Statutory Federal Rate

A reconciliation of the expected federal income tax at the statutory rate to the provision for income taxes was as follows (in thousands):

	Year Ended December 31,
	2018			2017			2016
Expected federal income tax at statutory rate	$	5,951		$	3,635		$	2,662
State income taxes, net of federal tax effect		1,293			417			284
Tax impact of foreign activity		57			(105	)		(115	)
Nondeductible executive compensation		902			530			159
Nondeductible expenses		351			268			213
Change in valuation allowance		(4	)		16			(35	)
Change in state deferred rate		38			(134	)		(67	)
Research and development credit		(1,843	)		(227	)		(261	)
Tax impact of Tax Cuts and Jobs Act		—			6,796			—
Tax impact of stock activity		(2,438	)		(925	)		—
Other		161			71			(85	)
Total provision for income taxes	$	4,468		$	10,342		$	2,755

Significant Components of Deferred Tax Assets (Liabilities)

The significant components of our deferred tax assets (liabilities) were as follows (in thousands):

	December 31,
	2018						2017
Deferred tax assets
Net operating loss and credit carryforwards	$	8,356					$	11,067
Stock-based compensation expense		3,647						4,273
Accounts receivable allowances		464						307
Accrued expenses		3,185						2,126
Other		180						182
Gross deferred tax asset					15,832						17,955
Less: valuation allowance		(797	)					(602	)
Total net deferred tax asset					15,035						17,353
Deferred tax liability
Deferred operations		(2,787	)					(3,850	)
Foreign operations		(135	)					(133	)
Depreciation and amortization		(2,943	)					(1,536	)
Other		(90	)					(24	)
Total deferred tax liability					(5,955	)					(5,543	)
Net deferred tax assets				$	9,080					$	11,810

Net Income Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Components of Computation of Basic and Diluted Net Income Per Share

The following table presents the components of the computation of basic and diluted net income per share for the periods indicated (in thousands, except per share amounts):

	Year Ended December 31,
	2018		2017		2016
Numerator
Net income	$	23,872	$	351	$	4,963
Denominator
Weighted average common shares outstanding, basic		17,196		17,183		16,947
Options to purchase common stock		306		150		267
Restricted stock units		104		23		27
Weighted average common shares outstanding, diluted		17,606		17,356		17,241
Net income per share
Basic	$	1.39	$	0.02	$	0.29
Diluted	$	1.36	$	0.02	$	0.29

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summary of Unaudited Quarterly Statements of Comprehensive Income Data

The following table presents our selected unaudited quarterly statements of comprehensive income data (in thousands, except per share amounts):

	For the Three Months Ended
2018	Mar 31		Jun 30		Sep 30		Dec 31
Revenues	$	59,092	$	61,091	$	62,868	$	65,189
Gross profit		39,334		40,689		42,457		44,012
Income from operations		4,300		5,965		8,257		8,209
Net income		3,254		5,416		8,061		7,141
Diluted earnings per share	$	0.19	$	0.31	$	0.45	$	0.40

	For the Three Months Ended
2017	Mar 31		Jun 30		Sep 30		Dec 31
Revenues	$	51,879	$	54,092	$	56,057	$	58,057
Gross profit		34,549		35,901		37,412		38,598
Income from operations		3,379		2,956		3,354		292
Net income (loss)		2,985		1,968		2,176		(6,778	)
Diluted earnings per share	$	0.17	$	0.11	$	0.13	$	(0.39	)

General - Additional Information (Detail) $ in Millions	12 Months Ended
General - Additional Information (Detail) $ in Millions	Dec. 31, 2018 Segment	Jan. 01, 2019 USD ($)
Schedule Of Accounting Policies [Line Items]
Number of reportable segments \| Segment	1
Deferred commission expected amortization period	2 years
ASU 2016-02 [Member] \| Subsequent Event [Member]
Schedule Of Accounting Policies [Line Items]
Operating leases, right of use assets		$ 15.0
Operating leases, lease liabilities		$ 15.0
Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Hosting services arrangement period	4 years
Minimum [Member] \| Subscriber Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	3 years
Minimum [Member] \| Non-competition Agreements [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	2 years
Minimum [Member] \| Technology and Other [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	1 year
Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Hosting services arrangement period	5 years
Maximum [Member] \| Subscriber Relationships [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	10 years
Maximum [Member] \| Non-competition Agreements [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	5 years
Maximum [Member] \| Technology and Other [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of intangible assets	10 years
Computer Equipment and Software [Member] \| Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	2 years
Computer Equipment and Software [Member] \| Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	3 years
Office Equipment and Furniture [Member] \| Minimum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	5 years
Office Equipment and Furniture [Member] \| Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Estimated useful lives of property and equipment	7 years

General - Audited Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Deferred costs	$ 34,502	$ 29,966
Deferred costs, non-current	10,973	9,967
Deferred income tax asset	10,456	13,697
LIABILITIES
Accrued compensation	20,415	15,228
Deferred revenue	25,328	17,863
Deferred revenue, non-current	2,512	2,731
STOCKHOLDERS’ EQUITY
Accumulated deficit	$ 15,261	(8,611)
ASU 2014-09 [Member] \| As Previously Reported [Member]
ASSETS
Deferred costs		25,091
Deferred costs, non-current		6,770
Deferred income tax asset		17,551
LIABILITIES
Accrued compensation		15,886
Deferred revenue		16,407
Deferred revenue, non-current		10,602
STOCKHOLDERS’ EQUITY
Accumulated deficit		(19,902)
ASU 2014-09 [Member] \| Adjustments [Member]
ASSETS
Deferred costs		4,875
Deferred costs, non-current		3,197
Deferred income tax asset		(3,854)
LIABILITIES
Accrued compensation		(658)
Deferred revenue		1,456
Deferred revenue, non-current		(7,871)
STOCKHOLDERS’ EQUITY
Accumulated deficit		$ 11,291

General - Audited Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues	$ 65,189	$ 62,868	$ 61,091	$ 59,092	$ 58,057	$ 56,057	$ 54,092	$ 51,879	$ 248,240	$ 220,085	$ 193,153
Operating expenses
Sales and marketing									71,719	71,261	66,876
Income from operations	8,209	8,257	5,965	4,300	292	3,354	2,956	3,379	26,731	9,981	6,385
Income tax expense									4,468	10,342	2,755
Net income (loss)	$ 7,141	$ 8,061	$ 5,416	$ 3,254	$ (6,778)	$ 2,176	$ 1,968	$ 2,985	$ 23,872	$ 351	$ 4,963
Net income per share
Basic									$ 1.39	$ 0.02	$ 0.29
Diluted	$ 0.40	$ 0.45	$ 0.31	$ 0.19	$ (0.39)	$ 0.13	$ 0.11	$ 0.17	$ 1.36	$ 0.02	$ 0.29
ASU 2014-09 [Member] \| As Previously Reported [Member]
Revenues										$ 220,566	$ 193,295
Operating expenses
Sales and marketing										73,295	65,886
Income from operations										8,428	7,517
Income tax expense										11,580	3,140
Net income (loss)										$ (2,440)	$ 5,710
Net income per share
Basic										$ (0.14)	$ 0.34
Diluted										$ (0.14)	$ 0.33
ASU 2014-09 [Member] \| Adjustments [Member]
Revenues										$ (481)	$ (142)
Operating expenses
Sales and marketing										(2,034)	990
Income from operations										1,553	(1,132)
Income tax expense										(1,238)	(385)
Net income (loss)										$ 2,791	$ (747)
Net income per share
Basic										$ 0.16	$ (0.05)
Diluted										$ 0.16	$ (0.04)

General - Audited Consolidated Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net income (loss)	$ 7,141	$ 8,061	$ 5,416	$ 3,254	$ (6,778)	$ 2,176	$ 1,968	$ 2,985	$ 23,872	$ 351	$ 4,963
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes									2,798	9,616	(2,083)
Changes in assets and liabilities
Deferred costs									(5,564)	(7,813)	(4,085)
Accrued compensation									3,957	1,304	2,291
Deferred revenue									7,094	5,588	2,852
Net cash provided by operating activities									$ 55,015	31,050	18,765
ASU 2014-09 [Member] \| As Previously Reported [Member]
Cash flows from operating activities
Net income (loss)										(2,440)	5,710
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes										10,854	(1,698)
Changes in assets and liabilities
Deferred costs										(6,548)	(4,964)
Accrued compensation										2,073	2,180
Deferred revenue										5,107	2,710
Net cash provided by operating activities										31,050	18,765
ASU 2014-09 [Member] \| Adjustments [Member]
Cash flows from operating activities
Net income (loss)										2,791	(747)
Reconciliation of net income to net cash provided by operating activities
Deferred income taxes										(1,238)	(385)
Changes in assets and liabilities
Deferred costs										(1,265)	879
Accrued compensation										(769)	111
Deferred revenue										$ 481	$ 142

Business Acquisitions - Additional Information (Detail) - USD ($)			3 Months Ended	12 Months Ended
	Dec. 18, 2018	Oct. 03, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Amortization expense for purchased intangible assets				$ 4,093,000	$ 4,574,000	$ 4,738,000
Stock issued for acquisition				3,371,000		$ 2,922,000
E D I Admin [Member]
Business Acquisition [Line Items]
Payments to acquire business		$ 7,461,000
Maximum payout of contingent consideration		$ 1,700,000
Amortization expense for purchased intangible assets			$ 100,000
E D I Admin [Member] \| Contingent Consideration Liability [Member]
Business Acquisition [Line Items]
Other expense				$ 100,000
CovalentWorks [Member]
Business Acquisition [Line Items]
Payments to acquire business	$ 19,431,000
Stock issued for acquisition	$ 3,371,000
Stock issued for acquisition, Shares	40,478

Business Acquisitions - Business Purchase Price (Detail) - USD ($) $ in Thousands			12 Months Ended
	Dec. 18, 2018	Oct. 03, 2018	Dec. 31, 2018	Dec. 31, 2016
Business Acquisition [Line Items]
SPS Commerce, Inc. common stock			$ 3,371	$ 2,922
E D I Admin [Member]
Business Acquisition [Line Items]
Cash		$ 7,461
Fair value of earn-out liability		1,274
Total purchase price		$ 8,735
CovalentWorks [Member]
Business Acquisition [Line Items]
Cash	$ 19,431
SPS Commerce, Inc. common stock	3,371
Total purchase price	$ 22,802

Business Acquisitions - Estimated Fair Values of Assets Acquired and Liabilities Assumed at Acquisition Date (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 18, 2018	Oct. 03, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net
Goodwill	$ 69,658			$ 51,613	$ 49,777
E D I Admin [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net
Current assets			$ 631
Goodwill			4,871
Intangible assets			3,400
Current liabilities			(57)
Deferred revenue			(110)
Total purchase price			$ 8,735
CovalentWorks [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net
Current assets		$ 244
Property and equipment		44
Goodwill		15,402
Intangible assets		7,210
Current liabilities		(56)
Deferred revenue		(42)
Total purchase price		$ 22,802

Business Acquisitions - Estimated Fair Value of Purchased Intangible Assets and Estimated Useful Lives (Detail) - USD ($) $ in Thousands	Dec. 18, 2018	Oct. 03, 2018
E D I Admin [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 3,400
E D I Admin [Member] \| Subscriber Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 600
Estimated Life (in years)		10 years
E D I Admin [Member] \| Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value		$ 2,800
Estimated Life (in years)		10 years
CovalentWorks [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 7,210
CovalentWorks [Member] \| Subscriber Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 7,100
Estimated Life (in years)	7 years
CovalentWorks [Member] \| Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 100
Estimated Life (in years)	3 years
CovalentWorks [Member] \| Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 10
Estimated Life (in years)	1 year

Revenue - Summary of Revenues by Revenue Stream (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Recognition [Line Items]
Revenues	$ 65,189	$ 62,868	$ 61,091	$ 59,092	$ 58,057	$ 56,057	$ 54,092	$ 51,879	$ 248,240	$ 220,085	$ 193,153
Recurring Revenues [Member]
Revenue Recognition [Line Items]
Revenues									230,654	203,920	177,057
One-time Revenues [Member]
Revenue Recognition [Line Items]
Revenues									17,586	16,165	16,096
Fulfillment [Member] \| Recurring Revenues [Member]
Revenue Recognition [Line Items]
Revenues									190,783	164,682	139,645
Analytics [Member] \| Recurring Revenues [Member]
Revenue Recognition [Line Items]
Revenues									34,447	34,260	32,938
Other [Member] \| Recurring Revenues [Member]
Revenue Recognition [Line Items]
Revenues									$ 5,424	$ 4,978	$ 4,474

Revenue - Additional Information (Detail)	12 Months Ended
Revenue - Additional Information (Detail)	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Earliest timing of billings	in advance
Latest timing of billings	30 days
Estimated period for material rights present to customers	2 years
Set up fees recognized period	2 years
Maximum recognition period for miscellaneous one-time fee	1 year
Analytics Solution [Member]
Disaggregation Of Revenue [Line Items]
Set up fees recognized period	1 year
Minimum [Member]
Disaggregation Of Revenue [Line Items]
Customer contract cancellation period	30 days
Current amount recognition period of set up fees	1 month
Long term amount recognition period of set up fees	13 months
Maximum [Member]
Disaggregation Of Revenue [Line Items]
Customer contract cancellation period	90 days
Deferred revenue recognition period	1 year
Contract period for remaining performance obligations for contracts in which the optional exemption under ASC 606-10-50-14(a) was applied	1 year
Current amount recognition period of set up fees	12 months
Long term amount recognition period of set up fees	24 months

Revenue - Summary of Deferred Revenue Liability Relating to Set-Up Fees (Detail) - Set-Up Fees [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Balances, at beginning of period	$ 10,031	$ 9,995
Invoiced set-up fees	10,271	10,625
Amortized set-up fees	(10,445)	(10,589)
Balances, at end of period	$ 9,857	$ 10,031

Deferred Costs - Additional Information (Detail)	12 Months Ended
Deferred Costs - Additional Information (Detail)	Dec. 31, 2018
Deferred Costs [Abstract]
Deferred commission expected amortization period	2 years

Deferred Costs - Summary of Deferred Costs and Amortization of Deferred Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs [Abstract]
Balances, at beginning of period	$ 39,933	$ 32,117
Incurred deferred costs	49,583	44,628
Amortized deferred costs	(44,041)	(36,812)
Balances, at end of period	$ 45,475	$ 39,933

Financial Instruments - Summary of Cash Equivalents and Short and Long-term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial Instruments [Member]
Schedule of Financial Instruments [Line Items]
Due within one year	$ 153,802	$ 144,736
Amortized Cost	153,648	149,953
Due within two years		5,206
Unrealized Gains (Losses)	154	(11)
Fair Value	153,802	149,942
Money Market Funds [Member]
Schedule of Financial Instruments [Line Items]
Amortized Cost	109,265	104,544
Fair Value	109,265	104,544
Certificate of Deposit [Member]
Schedule of Financial Instruments [Line Items]
Amortized Cost	7,000	7,814
Fair Value	7,000	7,814
Corporate Bonds [Member]
Schedule of Financial Instruments [Line Items]
Amortized Cost	15,194	17,758
Unrealized Gains (Losses)	40	(57)
Fair Value	15,234	17,701
Commercial Paper [Member]
Schedule of Financial Instruments [Line Items]
Amortized Cost	9,889	7,456
Unrealized Gains (Losses)	76	20
Fair Value	9,965	7,476
U.S. Treasury Securities [Member]
Schedule of Financial Instruments [Line Items]
Amortized Cost	12,300	12,381
Unrealized Gains (Losses)	38	26
Fair Value	$ 12,338	$ 12,407

Financial Instruments - Additional Information (Detail) - E D I Admin [Member]	Oct. 03, 2018 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maximum payout of contingent consideration	$ 1,700,000
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maximum payout of contingent consideration	$ 1,700,000

Financial Instruments - Summary of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	$ 153,802	$ 149,942
Liabilities fair value	1,368
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	109,265	104,544
Certificate of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	7,000	7,814
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	15,234	17,701
Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	9,965	7,476
U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	12,338	12,407
Earn-out Liability [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities fair value	1,368
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	116,265	112,358
Level 1 [Member] \| Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	109,265	104,544
Level 1 [Member] \| Certificate of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	7,000	7,814
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	37,537	37,584
Level 2 [Member] \| Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	15,234	17,701
Level 2 [Member] \| Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	9,965	7,476
Level 2 [Member] \| U.S. Treasury Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets fair value	12,338	$ 12,407
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities fair value	1,368
Level 3 [Member] \| Earn-out Liability [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities fair value	$ 1,368

Allowance for Doubtful Accounts - Schedule of Allowance for Doubtful Activity Included in Accounts Receivable Net (Detail) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balances, January 1	$ 763	$ 515	$ 446
Provision for doubtful accounts	2,590	1,705	1,375
Write-offs, net of recoveries	(1,961)	(1,457)	(1,306)
Balances, December 31	$ 1,392	$ 763	$ 515

Property and Equipment, net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 62,132	$ 50,807
Less: accumulated depreciation and amortization	(41,175)	(33,951)
Net, Total	20,957	16,856
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	44,781	35,326
Office Equipment and Furniture [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	7,985	7,439
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 9,366	$ 8,042

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Outside of U.S [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net held at subsidiary and office locations outside of the U.S.	$ 1.7	$ 2.2

Goodwill and Intangible Assets, net - Schedule of Changes in Net Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Balances, January 1	$ 51,613	$ 49,777
Additions from business acquisitions	20,272
Foreign currency translation	(2,227)	1,836
Balances, December 31	$ 69,658	$ 51,613

Goodwill and Intangible Assets, net - Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	$ 50,971	$ 38,979
Accumulated Amortization	(27,543)	(23,168)
Foreign Currency Translation	(687)	718
Net	22,741	16,529
Subscriber Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	43,212	34,350
Accumulated Amortization	(23,284)	(19,592)
Foreign Currency Translation	(623)	614
Net	19,305	15,372
Non-competition Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	2,560	2,499
Accumulated Amortization	(2,247)	(2,058)
Foreign Currency Translation	(28)	45
Net	285	486
Technology and Other [Member]
Finite-Lived Intangible Assets [Line Items]
Carrying Amount	5,199	2,130
Accumulated Amortization	(2,012)	(1,518)
Foreign Currency Translation	(36)	59
Net	$ 3,151	$ 671

Goodwill and Intangible Assets, net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 4,093	$ 4,574	$ 4,738

Goodwill and Intangible Assets, net - Future Amortization Expense for Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
2019	$ 5,026
2020	4,679
2021	3,845
2022	2,742
2023	2,668
Thereafter	3,781
Net	$ 22,741	$ 16,529

Other Assets - Summary of Changes in Net Amount of Capitalized Implementation Costs for Internal-use Software from Hosting Arrangements (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Capitalized Computer Software Net [Abstract]
Capitalized implementation fees	$ 455
Ending balance	$ 455

Other Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Capitalized Computer Software Net [Abstract]
Impairment losses on capitalized implementation costs	$ 0	$ 0

Commitments and Contingencies - Additional Information (Detail) $ in Millions		12 Months Ended
	Dec. 20, 2017 ft² Option	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2020 ft²
Commitments And Contingencies [Line Items]
Rent expense charged to operations		$ 5.6	$ 4.9	$ 5.0
Current Headquarters [Member]
Commitments And Contingencies [Line Items]
Lease agreement expires, date	Apr. 30, 2025
Number of options to extend term of the lease \| Option	2
Lease extension period, number of years	5 years
Incentives received upon execution of amendment		3.2
Incentives Owed Upon Expansion of Square Footage		$ 2.1
Current Headquarters [Member] \| Minneapolis, Minnesota [Member]
Commitments And Contingencies [Line Items]
Current leased space for headquarters \| ft²	189,000
Current Headquarters [Member] \| Scenario, Forecast [Member] \| Minneapolis, Minnesota [Member]
Commitments And Contingencies [Line Items]
Future expansion of headquarters premises \| ft²					25,000

Commitments and Contingencies - Future Minimum Payments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 4,209
2020	3,542
2021	4,414
2022	4,042
2023	3,854
Thereafter	4,817
Operating leases, total	$ 24,878

Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Dec. 18, 2018	Nov. 02, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Stockholders Equity [Line Items]
Stock issued for acquisition			$ 3,371		$ 2,922
Treasury stock at cost			$ 19,864	$ 5,815
Common Stock [Member]
Schedule Of Stockholders Equity [Line Items]
Stock issued for acquisition, Shares			40,478		43,953
Stock repurchase program, authorized amount		$ 50,000
Stock repurchase program, period		2 years
Repurchase of treasury shares			(289,745)	(122,147)
Stock repurchase program, available for future repurchases			$ 24,300
CovalentWorks [Member]
Schedule Of Stockholders Equity [Line Items]
Stock issued for acquisition, Shares	40,478
Stock issued for acquisition	$ 3,371

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2018	Feb. 28, 2017 shares	Dec. 31, 2018 USD ($) Offering $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Jan. 31, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant \| shares			5,300,000
Stock-based compensation expense			$ 12,510	$ 12,727	$ 8,023
Unrecognized stock-based compensation expense			$ 13,600
Unrecognized stock-based compensation, expected to be recognized, weighted average period			2 years 3 months 18 days
Fair value of options vested			$ 3,700	4,200	3,400
Intrinsic value of options exercised			14,900	2,800	8,600
Intrinsic value of options outstanding			$ 26,700	$ 7,300	$ 25,600
Weighted average fair value per share of options granted \| $ / shares			$ 19.48	$ 18.85	$ 16.13
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved for issuance under the plan \| shares			1,000,000
Stock-based compensation expense			$ 500	$ 700	$ 600
Number of offerings per year \| Offering			2
Amount withheld from employees			$ 1,700	$ 1,900	$ 1,700
Employee stock purchase plan, shares purchased \| shares			34,798	40,968	33,357
Maximum [Member] \| Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price as a percentage of fair market value			85.00%
Chief Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 3,600
Equity Incentive Plan [Member] \| 2010 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved for issuance under the plan \| shares		1,024,868				1,027,620
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 3,355	5,223	$ 3,777
Vesting period			4 years
Stock options exercisable \| shares			576,842
Weighted average exercise price \| $ / shares			$ 50.10
Weighted average remaining contractual life			4 years
Stock Options [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term range			7 years
Stock Options [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options contractual term range			10 years
Performance Share Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years	3 years
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 5,930	6,526	3,386
Vesting period			4 years
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 487	$ 318	$ 308
Restricted stock awards units vest over, period			1 year
Performance Share Units and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSU's vested and not issued during the period \| shares			54,688

Stock-Based Compensation - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 12,510	$ 12,727	$ 8,023
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	3,355	5,223	3,777
Performance Share Unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance Share Units	1,034
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	5,930	6,526	3,386
Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	487	318	308
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	466	660	552
401(k) Stock Match [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,238
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,168	1,887	1,309
Sales and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,675	2,197	2,412
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,505	949	618
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 6,162	$ 7,694	$ 3,684

Stock-Based Compensation - Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding, Beginning balance	1,097,331	1,016,012	943,103
Options, Granted	181,472	172,697	340,609
Options, Exercised	(344,334)	(65,502)	(221,630)
Options, Forfeited	(61,235)	(25,876)	(46,070)
Options Outstanding, Ending balance	873,234	1,097,331	1,016,012
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 47.60	$ 44.72	$ 37.91
Weighted Average Exercise Price, Granted	59.88	55.87	48.58
Weighted Average Exercise Price, Exercised	41.66	21.53	19.42
Weighted Average Exercise Price, Forfeited	56.67	55.93	55.58
Weighted Average Exercise Price, Outstanding, Ending Balance	$ 51.86	$ 47.60	$ 44.72

Stock-Based Compensation - Weighted Average Fair Value Per Share of Options Granted, Assumptions (Detail) - Stock Options [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	35.00%	38.00%	38.00%
Dividend yield	0.00%	0.00%	0.00%
Life (in years)	4 years 5 months 8 days	4 years 6 months 3 days	4 years 6 months 15 days
Risk-free interest rate	2.54%	1.85%	1.19%

Stock-Based Compensation - Performance Share Units and Restricted Stock Units (Detail) - Performance Share Units and Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards, Outstanding, Beginning Balance	321,912	189,042	140,565
Granted, stock units	172,795	211,168	115,896
Vested and common stock issued, stock units	(81,561)	(64,950)	(52,133)
Forfeited, stock units	(35,811)	(13,348)	(15,286)
Stock awards, Outstanding, Ending Balance	377,335	321,912	189,042
Weighted average grant date fair value, Outstanding, Beginning Balance	$ 55.16	$ 54.14	$ 56.88
Granted, Weighted Average Grant Date Fair Value	66.03	55.62	48.32
Vested and common stock issued, Weighted Average Grant Date Fair Value	56.32	53.64	48.19
Forfeited, Weighted Average Grant Date Fair Value	55.04	55.39	55.48
Weighted average grant date fair value, Outstanding, Ending Balance	$ 59.90	$ 55.16	$ 54.14

Stock-Based Compensation - Restricted Stock Awards (Detail) - Restricted Stock Award [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards, Outstanding, Beginning Balance	1,368	1,524	1,032
Restricted common stock issued, stock awards	7,304	5,454	6,078
Restrictions lapsed, stock awards	(6,840)	(5,610)	(5,586)
Stock awards, Outstanding, Ending Balance	1,832	1,368	1,524
Weighted average grant date fair value, Outstanding, Beginning Balance	$ 58.29	$ 52.28	$ 67.39
Restricted common stock issued, Weighted Average Grant Date Fair Value	74.43	58.29	52.27
Restrictions lapsed, Weighted Average Grant Date Fair Value	71.20	56.65	55.06
Weighted average grant date fair value, Outstanding, Ending Balance	$ 74.44	$ 58.29	$ 52.28

Stock-Based Compensation - Fair Value Estimation of Common Stock Using Black-Scholes Option Pricing Model, Weighted-Average Assumptions (Detail) - Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	26.00%	32.00%	37.00%
Dividend yield	0.00%	0.00%	0.00%
Life (in years)	6 months	6 months	6 months
Risk-free interest rate	1.77%	0.90%	0.42%

Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal		$ (184)	$ 3,684
State	$ 1,103	258	555
Foreign	540	652	599
Deferred
Federal	3,011	10,262	(1,337)
State	224	(291)	(169)
Foreign	(410)	(355)	(577)
Total provision for income taxes	$ 4,468	$ 10,342	$ 2,755

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Expense Benefit [Line Items]
Reclass of AMT credit carryforward to current federal expense		$ 400
Unutilized alternative minimum tax credit carryforwards partially refundable year one	2019
Unutilized alternative minimum tax credit carryforwards partially refundable year two	2020
Unutilized alternative minimum tax credit carryforwards partially refundable year three	2021
Unutilized alternative minimum tax credit carryforwards fully refundable year	2022
Tax expense related to The Job Cuts and Tax Act (“Tax Act”), primarily due to reduction in corporate tax rate		6,796
Corporate federal income tax rate	21.00%
Valuation allowance against our deferred tax assets	$ 797	$ 602
Domestic Tax Authority [Member]
Income Tax Expense Benefit [Line Items]
Net operating loss carryforward	$ 37,500
Expiration of net operating loss carryforwards	Loss carryforwards for federal tax purposes will expire between 2020 and 2038 if not utilized
Losses expected to expire unused	$ 17,600
Maximum annual limitation of federal net operating losses	1,000
Domestic Tax Authority [Member] \| Research and Development [Member]
Income Tax Expense Benefit [Line Items]
Research and development credit carryforwards	$ 3,000
Year in which credit carryforward begins to expire	2030
State and Local Jurisdiction [Member]
Income Tax Expense Benefit [Line Items]
Net operating loss carryforward	$ 4,100
Expiration of net operating loss carryforwards	Loss carryforwards for state tax purposes will expire between 2019 and 2031 if not utilized
State and Local Jurisdiction [Member] \| Net Operating Loss and Credit Carryforwards [Member]
Income Tax Expense Benefit [Line Items]
Valuation allowance against our deferred tax assets	$ 800
State and Local Jurisdiction [Member] \| Research and Development [Member]
Income Tax Expense Benefit [Line Items]
Research and development credit carryforwards	$ 1,000
Year in which credit carryforward begins to expire	2025

Income Taxes - Reconciliation of Provision for Income Taxes to Statutory Federal Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Expected federal income tax at statutory rate	$ 5,951	$ 3,635	$ 2,662
State income taxes, net of federal tax effect	1,293	417	284
Tax impact of foreign activity	57	(105)	(115)
Nondeductible executive compensation	902	530	159
Nondeductible expenses	351	268	213
Change in valuation allowance	(4)	16	(35)
Change in state deferred rate	38	(134)	(67)
Research and development credit	(1,843)	(227)	(261)
Tax impact of Tax Cuts and Jobs Act		6,796
Tax impact of stock activity	(2,438)	(925)
Other	161	71	(85)
Total provision for income taxes	$ 4,468	$ 10,342	$ 2,755

Income Taxes - Significant Components of Deferred Tax Assets (Liabilities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Net operating loss and credit carryforwards	$ 8,356	$ 11,067
Stock-based compensation expense	3,647	4,273
Accounts receivable allowances	464	307
Accrued expenses	3,185	2,126
Other	180	182
Gross deferred tax asset	15,832	17,955
Less: valuation allowance	(797)	(602)
Total net deferred tax asset	15,035	17,353
Deferred tax liability
Deferred operations	(2,787)	(3,850)
Foreign operations	(135)	(133)
Depreciation and amortization	(2,943)	(1,536)
Other	(90)	(24)
Total deferred tax liability	(5,955)	(5,543)
Net deferred tax assets	$ 9,080	$ 11,810

Net Income Per Share - Components of Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net income	$ 7,141	$ 8,061	$ 5,416	$ 3,254	$ (6,778)	$ 2,176	$ 1,968	$ 2,985	$ 23,872	$ 351	$ 4,963
Denominator
Weighted average common shares outstanding, basic									17,196	17,183	16,947
Options to purchase common stock									306	150	267
Restricted stock units									104	23	27
Weighted average common shares outstanding, diluted									17,606	17,356	17,241
Net income per share
Basic									$ 1.39	$ 0.02	$ 0.29
Diluted	$ 0.40	$ 0.45	$ 0.31	$ 0.19	$ (0.39)	$ 0.13	$ 0.11	$ 0.17	$ 1.36	$ 0.02	$ 0.29

Net Income Per Share - Additional Information (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income per share
Outstanding potential common shares excluded from calculation of diluted net income (loss) per share	1	283	5

Retirement Savings Plan - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Maximum allowable contribution by employee percentage	100.00%
Defined benefit plan employer matching contribution percent	50.00%
Maximum annual contribution per employee, percent	6.00%
Employer matching contribution amount	$ 2,900	$ 1,600	$ 1,400
Stock-based compensation expense	12,510	$ 12,727	$ 8,023
401(k) Stock Match [Member]
Defined Contribution Plan Disclosure [Line Items]
Stock-based compensation expense	$ 1,238

Related Party Transactions - Additional Information (Detail) - SPS Commerce Foundation [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Contributions to Foundation	$ 700,000	$ 200,000
Legal obligations for future commitments to Foundation	0
Directors of Foundation [Member]
Related Party Transaction [Line Items]
Officers' compensation from Foundation	$ 0

Selected Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Statements of Comprehensive Income Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 65,189	$ 62,868	$ 61,091	$ 59,092	$ 58,057	$ 56,057	$ 54,092	$ 51,879	$ 248,240	$ 220,085	$ 193,153
Gross profit	44,012	42,457	40,689	39,334	38,598	37,412	35,901	34,549	166,492	146,460	128,807
Income from operations	8,209	8,257	5,965	4,300	292	3,354	2,956	3,379	26,731	9,981	6,385
Net income (loss)	$ 7,141	$ 8,061	$ 5,416	$ 3,254	$ (6,778)	$ 2,176	$ 1,968	$ 2,985	$ 23,872	$ 351	$ 4,963
Diluted earnings per share	$ 0.40	$ 0.45	$ 0.31	$ 0.19	$ (0.39)	$ 0.13	$ 0.11	$ 0.17	$ 1.36	$ 0.02	$ 0.29

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details