Stamps.com (STMP) 10-Q 7 May 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	000-26427
Entity Registrant Name	Stamps.com Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0454966
Entity Address, Address Line One	1990 E. Grand Avenue
Entity Address, City or Town	El Segundo
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90245
City Area Code	310
Local Phone Number	482-5800
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	STMP
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		18,319,142
Entity Central Index Key	0001082923
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 567,471	$ 443,552
Accounts receivable, net	47,600	63,308
Current income taxes	610	8,035
Prepaid expenses	14,467	17,480
Other current assets	68,645	86,319
Total current assets	698,793	618,694
Property and equipment, net	36,021	32,887
Goodwill	390,353	388,753
Intangible assets, net	120,635	125,254
Deferred income taxes, net	26,371	26,378
Lease right-of-use assets	56,348	58,506
Other assets	20,734	46,827
Total assets	1,349,255	1,297,299
Current liabilities:
Accounts payable and other current liabilities	230,962	215,967
Deferred revenue	7,411	7,833
Current portion of lease right-of-use liabilities	4,956	6,285
Total current liabilities	243,329	230,085
Deferred income taxes, net	7,701	7,524
Long-term portion of lease right-of-use liabilities	54,894	53,986
Other liabilities	32,709	31,585
Total liabilities	338,633	323,180
Commitments and contingencies (Note 2)
Stockholders' equity:
Common stock, $0.001 par value per share; Authorized shares: 47,500 in 2021 and 2020; Issued shares: 34,906 in 2021 and 34,707 in 2020; Outstanding shares: 18,369 in 2021 and 18,306 in 2020	57	57
Additional paid-in capital	1,302,865	1,276,484
Treasury stock, at cost, 16,537 shares in 2021 and 16,401 shares in 2020	(675,163)	(648,132)
Retained earnings	363,850	329,606
Accumulated other comprehensive income (loss)	19,013	16,104
Total stockholders' equity	1,010,622	974,119
Total liabilities and stockholders' equity	$ 1,349,255	$ 1,297,299
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Mar. 31, 2021	Dec. 31, 2020
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	47,500	47,500
Common stock, shares issued (in shares)	34,906	34,707
Common stock, shares outstanding (in shares)	18,369	18,306
Treasury stock, shares (in shares)	16,537	16,401

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Revenues	$ 189,090	$ 151,346
Cost of revenues (exclusive of amortization of intangible assets, which is included in general and administrative expense):
Total cost of revenues	43,223	40,380
Gross profit	145,867	110,966
Operating expenses:
Sales and marketing	43,866	37,004
Research and development	28,510	21,323
General and administrative	29,170	28,468
Total operating expenses	101,546	86,795
Income from operations	44,321	24,171
Foreign currency exchange gain (loss), net	(89)	(138)
Interest expense	(95)	(467)
Interest income and other income (loss), net	28	26
Income before income taxes	44,165	23,592
Income tax (benefit) expense	9,921	7,098
Net income	$ 34,244	$ 16,494
Net income per share:
Basic (in dollars per share)	$ 1.86	$ 0.97
Diluted (in dollars per share)	$ 1.74	$ 0.91
Weighted average shares outstanding:
Basic (in shares)	18,362	17,064
Diluted (in shares)	19,644	18,189
Service
Revenues:
Revenues	$ 179,020	$ 139,136
Cost of revenues (exclusive of amortization of intangible assets, which is included in general and administrative expense):
Total cost of revenues	41,375	36,527
Product
Revenues:
Revenues	5,513	5,956
Cost of revenues (exclusive of amortization of intangible assets, which is included in general and administrative expense):
Total cost of revenues	1,848	1,738
Insurance
Revenues:
Revenues	4,557	3,180
Customized postage
Revenues:
Revenues	0	3,074
Cost of revenues (exclusive of amortization of intangible assets, which is included in general and administrative expense):
Total cost of revenues	$ 0	$ 2,115

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 34,244	$ 16,494
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	2,909	(14,727)
Comprehensive income	$ 37,153	$ 1,767

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Treasury Stock at Cost	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Dec. 31, 2019		17,029
Beginning Balance at Dec. 31, 2019	$ 665,625	$ 56	$ 1,098,426	$ (593,511)	$ 150,941	$ 9,713
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,494				16,494
Other comprehensive income (loss)	(14,727)					(14,727)
Stock-based compensation expense	10,725		10,725
Exercise of stock options (in shares)		103
Exercise of stock options	8,818		8,818
Shares issued under the Employee Stock Purchase Plan (in shares)		50
Shares issued under the Employee Stock Purchase Plan	$ 1,950		1,950
Stock repurchase (in shares)	(80)	(80)
Stock repurchase	$ (8,577)			(8,577)
Ending Balance (in shares) at Mar. 31, 2020		17,102
Ending Balance at Mar. 31, 2020	$ 680,308	$ 56	1,119,919	(602,088)	167,435	(5,014)
Beginning Balance (in shares) at Dec. 31, 2020	18,306	18,306
Beginning Balance at Dec. 31, 2020	$ 974,119	$ 57	1,276,484	(648,132)	329,606	16,104
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	34,244				34,244
Other comprehensive income (loss)	2,909					2,909
Stock-based compensation expense	8,690		8,690
Exercise of stock options (in shares)		186
Exercise of stock options	15,237		15,237
Shares issued under the Employee Stock Purchase Plan (in shares)		13
Shares issued under the Employee Stock Purchase Plan	$ 2,454		2,454
Stock repurchase (in shares)	(136)	(136)
Stock repurchase	$ (27,031)			(27,031)
Ending Balance (in shares) at Mar. 31, 2021	18,369	18,369
Ending Balance at Mar. 31, 2021	$ 1,010,622	$ 57	$ 1,302,865	$ (675,163)	$ 363,850	$ 19,013

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net income	$ 34,244	$ 16,494
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,443	6,588
Stock-based compensation expense	8,690	10,725
Accretion of debt issuance costs	96	93
Changes in operating assets and liabilities, net of assets and liabilities acquired:
Accounts receivable	15,966	18,645
Prepaid expenses	3,071	3,102
Other current assets	17,675	(6,110)
Current income taxes	7,438	69
Lease right-of-use assets	2,238	1,024
Other assets	26,003	(7,304)
Deferred revenue	(460)	(18)
Lease right-of-use liabilities	(497)	(827)
Other liabilities	1,169	929
Accounts payable and other current liabilities	14,938	3,248
Net cash provided by operating activities	137,014	46,658
Investing activities:
Acquisition of property and equipment	(1,233)	(1,921)
Net cash used in investing activities	(1,233)	(1,921)
Financing activities:
Net proceeds from (repayments of) short-term financing obligations	(2,636)	15,665
Principal payments on term loan	0	(3,093)
Proceeds from exercise of stock options	15,237	8,818
Issuance of common stock under Employee Stock Purchase Plan	2,454	1,950
Repurchase of common stock	(27,031)	(8,577)
Net cash provided by (used in) financing activities	(11,976)	14,763
Effect of exchange rate changes	114	(183)
Net increase (decrease) in cash and cash equivalents	123,919	59,317
Cash and cash equivalents at beginning of period	443,552	156,307
Cash and cash equivalents at end of period	567,471	215,624
Supplemental information:
Capital expenditures accrued but not paid at period end	3,138	0
Cash paid for amounts included in the measurement of lease liabilities included in cash provided by operating activities	857	1,275
Lease liabilities arising from obtaining right-of-use assets	$ 0	$ 852

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation We prepared the consolidated financial statements included herein pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with United States (US) generally accepted accounting principles (GAAP) have been condensed or omitted pursuant to such rules and regulations. We believe that the disclosures are adequate to make the information presented not misleading. We recommend that these consolidated financial statements be read in conjunction with the audited consolidated financial statements and the notes thereto included in our latest annual report on Form 10-K for the fiscal year ended December 31, 2020, filed with the SEC on February 26, 2021. In our opinion, these unaudited consolidated financial statements contain all adjustments (consisting only of normal recurring adjustments) considered necessary to present fairly our financial position as of March 31, 2021, our results of operations for the three months ended March 31, 2021, and our cash flows for the three months ended March 31, 2021. The results of operations for the interim period are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021. Basis of Consolidation The consolidated financial statements include all the assets, liabilities, revenues, expenses and cash flows of Stamps.com Inc. and the entities in which we have 100% voting and/or economic control. References in this Report to "we" "us" "our" or "Company" are references to Stamps.com Inc. and its subsidiaries. Intercompany accounts and transactions between consolidated entities have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with US GAAP requires us to make estimates, judgments and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes. Actual results could differ from those estimates, and such differences may be material to the consolidated financial statements. There are significant estimates and judgments inherent in the preparation of the consolidated financial statements including those related to the fair value of intangible assets and goodwill and the allowance for credit losses. The Company considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts on the consolidated financial statements for the period ended March 31, 2021. As events continue to evolve and additional information becomes available, our assumptions and estimates may change materially in future periods. Accounts Receivable Our accounts receivable relate to mailing and shipping services, postage purchasing and invoicing, branded insurance provided to customers prior to billing, and other receivables. We maintain an allowance for credit losses for expected uncollectible accounts which is recorded as an offset to accounts receivable and changes in such are classified as general and administrative expense in the consolidated statements of operations. We evaluate collectability by reviewing accounts receivable on a collective basis where similar characteristics exist and on an individual basis when we identify specific customers with known collectability issues. The evaluation is based on a combination of factors. If we become aware of a customer’s inability to meet its financial obligations, an allowance is recorded to reduce the net receivable to the amount reasonably believed to be collectible from the customer. Accounts receivable are written off against the allowance for uncollectible accounts when we determine amounts are no longer collectible. We recognize allowances for credit losses for all other customers based on either the age of the receivable or applying a loss rate method which incorporates historical experience and an evaluation of macroeconomic factors, including the estimated impact of COVID-19 on the collectability of our accounts receivable. As additional information becomes available to us, our future assessment of our allowance for credit losses could materially and adversely impact our consolidated financial statements in future reporting periods. There were no material write offs or recoveries against the allowance for uncollectible accounts during fiscal 2021 and 2020, respectively. The allowance for credit losses on accounts receivable was approximately $9.1 million and $11.9 million as of March 31, 2021 and December 31, 2020, respectively. Business Combinations The acquisition method of accounting is used for business combinations. The results of operations of acquired businesses are included in our consolidated financial statements prospectively from the date of acquisition. The fair value of purchase consideration is allocated to the assets acquired and liabilities assumed from the acquired entity and is generally based on their fair value at the acquisition date. The excess of the fair value of purchase consideration over the fair value of the assets acquired and liabilities assumed is recorded as goodwill. Acquisition-related expenses are recognized in our consolidated financial statements as incurred. Contingencies and Litigation In the ordinary course of business, we are subject to various litigation matters as a claimant and a defendant. We record any amounts recovered in these matters when received. We establish loss provisions for claims against us when the loss is both probable and can be reasonably estimated. If either or both of the criteria are not met, we assess whether there is at least a reasonable possibility that a loss, or additional losses, may have been incurred. If there is a reasonable possibility that a loss or additional loss may have been incurred for such proceedings, we disclose the estimate of the amount of loss or possible range of loss, or disclose that an estimate of loss cannot be made, as applicable. Deferred Revenue Our deferred revenue relates mainly to service revenue, which generally arises due to the timing of payment versus the provision of services for certain customers billed in advance. Approximately $5.9 million of revenue recognized in the three months ended March 31, 2021 was included in the deferred revenue balance at December 31, 2020. Approximately $6.4 million of revenue recognized in the three months ended March 31, 2020 was included in the deferred revenue balance at December 31, 2019. Fair Value of Financial Instruments Carrying amounts of certain of our financial instruments, including cash and cash equivalents, accounts receivable and accounts payable, approximate fair value due to their short maturities. When drawn, the Company's outstanding debt held by third party financial institutions is carried at cost, adjusted for debt issuance costs. When drawn, the Company's debt is not publicly traded and the carrying amount typically approximates fair value for debt that accrues interest at a variable rate for companies with similar financial characteristics as the Company, which are considered Level 2 fair value inputs as defined in Note 7 - "Fair Value Measurements" in our consolidated financial statements. Foreign Currency Translation The functional currency of the Company’s major foreign subsidiaries is generally the local currency. Adjustments resulting from translating foreign functional currency financial statements into US dollars are recorded in accumulated other comprehensive income as a component of stockholders’ equity. Foreign currency transaction gains and losses are included in foreign currency exchange gain (loss), net. All assets and liabilities denominated in a foreign currency are translated into US dollars at the exchange rate on the balance sheet date. Revenues and expenses are translated at the average exchange rate during the period. Goodwill and Indefinite-Lived Intangible Assets Goodwill represents the excess of the fair value of consideration given over the fair value of the tangible assets, identifiable intangible assets and liabilities assumed in business combinations. We are required to test goodwill for impairment annually and whenever events or circumstances indicate the fair value of a reporting unit may be below its carrying value. A reporting unit is the operating segment or a business that is one level below that operating segment. Reporting units are aggregated as a single reporting unit if they have similar economic characteristics. Goodwill is reviewed for impairment annually on October 1 utilizing either a qualitative or quantitative assessment. We have an option to make a qualitative assessment of a reporting unit's goodwill for impairment. If we choose to perform a qualitative assessment and determine the fair value more likely than not exceeds the carrying value, no further evaluation is necessary. When we perform a quantitative assessment, we compare the fair value of the reporting unit, which we primarily determine using an income approach based on the present value of discounted cash flows, to the respective carrying value, which includes goodwill. If the fair value of the reporting unit exceeds its carrying value, the goodwill is not considered impaired. If the carrying value is higher than the fair value, the difference is recognized as an impairment loss. As of March 31, 2021, we are not aware of any indicators of impairment that would require an impairment analysis other than our annual goodwill impairment analysis. No instances of impairment to the Company's goodwill were identified during our October 1, 2020 review. Indefinite-lived intangible assets are reviewed for impairment annually on October 1 and whenever events or circumstances indicate that the fair value of an indefinite-lived intangible asset may be below its carrying value. In assessing other intangible assets not subject to amortization for impairment, the Company also has the option to perform a qualitative assessment to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of such an intangible asset is less than its carrying amount. If the Company determines that it is not more likely than not that the fair value of such an intangible asset is less than its carrying amount, then the Company is not required to perform any additional tests for assessing those intangible assets for impairment. However, if the Company concludes otherwise or elects not to perform the qualitative assessment, then it is required to perform a quantitative impairment test that involves a comparison of the estimated fair value of the intangible asset with its carrying value. If the carrying value of the intangible asset exceeds its fair value, an impairment loss is recognized in an amount equal to that excess. As of March 31, 2021, we are not aware of any indicators of impairment that would require an impairment analysis other than our annual indefinite-lived intangible assets impairment analysis. The Company concluded that it was more likely than not the fair value of each of the Company's intangible assets not subject to amortization was in excess of its respective carrying value during our October 1, 2020 review. Long-Lived Assets and Finite-Lived Intangible Assets Long-lived assets including intangible assets with finite useful lives are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. We account for property and equipment at cost less accumulated depreciation and amortization. We compute depreciation using the straight-line method over the estimated useful life of the asset, generally three ten Income Taxes We are subject to income taxes in the US and foreign jurisdictions. We provide for income taxes at the current and future enacted tax rate and consistent with the laws applicable in each jurisdiction. We account for income taxes in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic No. 740, Income Taxes ( Income Taxes ), which requires that deferred tax assets and liabilities be recognized using enacted tax rates for the effect of temporary differences between the book and tax basis of recorded assets and liabilities. Income Taxes also requires that deferred tax assets be reduced by a valuation allowance if it is more likely than not that some or all of the net deferred tax assets will not be realized. We record a valuation allowance to reduce our gross deferred tax assets to the amount that is more likely than not (a likelihood of more than 50 percent) to be realized. In order for us to realize our deferred tax assets, we must be able to generate sufficient taxable income. We evaluate the appropriateness of our deferred tax assets and related valuation allowance in accordance with Income Taxes based on all available positive and negative evidence. Leases We determine if an arrangement is a lease at inception. Right-of-use (ROU) assets and liabilities are recognized at the present value of the future lease payments at the lease commencement date. For this purpose, we consider only payments that are fixed and determinable at the time of commencement. As most of our leases do not provide an implicit rate, the interest rate used to determine the present value of future lease payments is an estimated incremental borrowing rate. Many of our leases include one or more options to renew. These options are factored into the determination of the lease term and lease payments when their exercise is considered to be reasonably certain. Our lease agreements generally contain lease and non-lease components. Non-lease components primarily include payments for maintenance and utilities. We elected the practical expedient to combine fixed payments for non-lease components with our lease payments and account for them together as a single lease component which increases the amount of the ROU assets and liabilities. We also elected to recognize the associated lease payments for leases with an initial term of 12 months or less in the consolidated statements of operations on a straight-line basis without recognizing a ROU asset or liability. Operating leases are included in lease right-of-use assets, current portion of lease right-of-use liabilities, and long-term portion of lease right-of-use liabilities on our consolidated balance sheets. Operating lease expense is recognized on a straight-line basis over the lease term in income from operations on our consolidated statements of operations. Other Current Assets Other current assets principally consist of prepayments for postage and shipping labels and inventory. Prepayments for postage and shipping labels totaled $64.5 million at March 31, 2021 and $82.4 million at December 31, 2020, respectively. Other Liabilities Other liabilities principally consist of long-term unrecognized income tax benefits, as well as indirect tax liabilities and other liabilities. Revenue Recognition We recognize revenues when we transfer control of promised goods or services to our customers in an amount that reflects the consideration to which we expect to be entitled to in exchange for those goods or services. We account for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance, and collectability of consideration is probable. Our payment terms vary by the products and services offered. The term between billings and when payment is due is not significant. Revenues are presented on a disaggregated basis on the consolidated statements of operations. Service revenue is recognized over time for each month that customers have access to our platform or at a point in time when assets are transferred to the customer. We earn service revenue from our mailing and shipping operations in several different ways: (1) customers may pay us a monthly fee, based on a subscription plan which may be waived or refunded for certain customers, for which we provide them access to our platform, in which case revenue is earned over the period of time that the customers have access to the platform which is typically month-to-month; (2) we may be compensated directly by our carriers for shipping labels printed that meet certain requirements, in which case revenue is earned over time, which is typically in the same month that the relevant labels are printed; (3) we may earn revenue from customers when they purchase postage, print shipping labels or perform other transactions using our solutions, in which case revenue is earned at the point in time we transfer an asset to the customer and have a present right of payment for the asset transferred; (4) we may earn revenue that may take the form of some or all of the spread between the rate a customer pays and the rate the carrier or integration partner receives, either charged directly or paid by our partners, in which case revenue is earned at a point in time, which is typically when the customer purchases postage or prints a shipping label; and (5) we may earn other types of revenue shares or other compensation from specific customers that have access to our platform or through integration partners, in which case revenue is recognized at a point in time, which is when we have fulfilled our performance obligations. In the case of monthly fees based on subscription plans, the Company recognizes a reduction of revenue in the period for which a waiver is granted or when a refund is processed, which is typically the same period in which the associated subscription revenue is recognized or, in the case of refunds, could be a later period. Waivers and refunds were not material to the consolidated financial statements during the three months ended March 31, 2021 or March 31, 2020, respectively. Customers may purchase delivery services from carriers through our mailing and shipping solutions. When funds are transferred directly from customers to the carrier, these funds are not recognized as revenue. We also provide mailing and shipping services for which the cost of postage or delivery is included in the cost of the service and, therefore, is recognized as service revenue. Product revenue consists of products sold through the mailing and shipping supplies stores which are available to our customers from within some of our mailing and shipping solutions. Products sold include mailing labels, shipping labels, thermal printers, scales, and other mailing and shipping-focused office supplies. We recognize product revenue on product purchases upon shipment of orders to customers. We provide our customers with the opportunity to purchase parcel insurance directly through our solutions. Insurance revenue represents the amount we receive from customers net of the costs paid to our insurance providers. We recognize insurance revenue on insurance purchases upon the ship date of the insured package, which is the point in time when we have fulfilled our performance obligations. Customized postage revenue, which includes the face value of postage, from the sale of customized postage sheets and rolls is recognized upon transfer of control of the product to the customer, which occurs upon our delivery to the carrier. In the second quarter of 2020, we received notification from the US Postal Service (USPS) that it was eliminating its customized postage program and also revoking our authorization to offer products pursuant to that program effective June 16, 2020. As a result, we do not expect material customized postage revenue or cost of revenue after June 2020. On a limited basis, we allow third parties to offer products and promotions to our customer base. These arrangements generally provide payment in the form of a flat fee or revenue sharing arrangements where we receive payment upon customers accessing third party products and services. Total revenue from such advertising arrangements was not significant during the three months ended March 31, 2021 or March 31, 2020, respectively. Segment Information Our operations consist of two segments: Stamps.com and Metapack. Please see Note 9 - “Segment and Geographical Information” in our Notes to Consolidated Financial Statements for further description. Short-Term Financing Obligations We utilize short-term financing, which is separate from our debt as described in Note 12 - "Debt," to fund certain Company operations. Short-term financing obligations are included in accounts payable and other current liabilities in the accompanying consolidated balance sheets. As of March 31, 2021, we had $12.4 million in short-term financing obligations and $57.6 million of unused credit. As of December 31, 2020, we had $15.1 million in short-term financing obligations and $57.0 million of unused credit. Stock-Based Compensation We account for share-based employee compensation plans under the fair value recognition and measurement provisions in accordance with applicable accounting standards, which require all share-based payments to employees, including grants of stock options and restricted stock units (RSUs), to be measured based on the grant date fair value of the awards, with the resulting expense generally recognized on a straight-line basis over the period during which the employee is required to perform service in exchange for the award. We account for forfeitures as they occur. We use the Black-Scholes-Merton option valuation model to estimate the fair value of share-based payment awards on the date of grant, which requires us to use a number of estimates and subjective assumptions, including stock price volatility, expected term, and risk-free interest rates. In the case of options we grant, our assumption of expected volatility is based on the historical volatility of our stock price over the term equal to the expected life of the options. We base the risk-free interest rate on US Treasury zero-coupon issues with a remaining term equal to the expected life of the options assumed at the date of grant. The estimated expected life represents the weighted average period the stock options are expected to remain outstanding, determined based on an analysis of historical exercise behavior. Trademarks, Trade Names, and Other Intangible Assets (excluding Goodwill) Acquired trademarks, trade names, and other intangibles (excluding goodwill) include both amortizable and non-amortizable assets and are included in intangible assets, net in the accompanying consolidated balance sheets. Intangible assets are carried at cost less accumulated amortization. Cost associated with internally developed intangible assets is typically expensed as incurred as research and development costs. Amortization of amortizable intangible assets is calculated on a straight-line basis, which is consistent with the expected future cash flows. Treasury Stock During the three months ended March 31, 2021 and March 31, 2020, we repurchased approximately 136,000 shares and 80,000 shares for $27.0 million and $8.6 million, respectively. Accounting Guidance Adopted in 2021 Income Taxes In December 2019, the FASB issued ASU 2019-12, a standard which eliminates certain exceptions to the general principles of ASC Topic 740 Income Taxes . The guidance became effective for the Company on January 1, 2021. The adoption of the guidance did not have a material impact on the Company's consolidated financial statements. Accounting Guidance Not Yet Adopted Reference Rate Reform In March 2020, the FASB issued 2020-04, optional accounting guidance for a limited period of time to ease the potential burden in accounting for reference rate reform. The new standard provides expedients and exceptions to existing accounting requirements for contract modifications and hedge accounting related to transitioning from discontinued reference rates, such as the London Interbank Offered Rate (LIBOR), to alternative reference rates, if certain criteria are met. The new standard was effective upon issuance and generally can be applied to applicable contract modifications through December 31, 2022. We are currently evaluating the impact of the transition from LIBOR to alternative reference interest rates on our Amended and Restated Credit Agreement, as described in Note 12 - " Debt ", but do not expect a significant impact to our operating results, financial position or cash flows.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings We are subject to various routine legal proceedings and claims incidental to our business, and we do not believe that these proceedings and claims would reasonably be expected to have a material adverse effect on our financial position, results of operations, or cash flows. On February 28, 2019 and March 13, 2019, two putative class action complaints were filed against us in the United States District Court for the Central District of California, Western Division. One of the two putative class actions was dismissed without prejudice, and in the other case, styled as Karinski v. Stamps.com, Inc. et al , Case 2:19-cv-01828 (the “Securities Class Action”), the Court appointed a lead plaintiff and approved lead plaintiff’s selection of lead counsel. Lead plaintiff filed a consolidated complaint in August 2019, purportedly on behalf of all those who purchased, or otherwise acquired, Stamps.com common stock between May 3, 2017 and May 8, 2019, alleging violations of the Securities Exchange Act of 1934 based on public disclosures that were purportedly rendered misleading based on certain uses of reseller rates. We filed a motion to dismiss in October 2019, and our motion to dismiss was granted in part and denied in part in January 2020. The Court granted plaintiff's motion for class certification on November 9, 2020, and the Court of Appeals granted our request to appeal that order on March 10, 2021. The parties are currently engaged in fact discovery with trial scheduled for March 2022. We believe that the case is without merit and intend to defend it vigorously. Due to the early stage of the case, neither the likelihood that a loss, if any, will be realized, nor an estimate of the possible loss or range of loss, if any, can be determined. On May 16, 2019 and May 21, 2019, two purported shareholder derivative suits were filed in the United States District Court for the Central District of California, Western Division, alleging breaches of fiduciary duties by officers and/or directors, unjust enrichment, abuse of control, waste of corporate assets, and violations of the Securities Exchange Act of 1934, and seeking unspecified damages, attorneys' fees and costs. The two cases were consolidated as In re Stamps.com Stockholder Derivative Litigation , Case 2:19-cv-04272 and co-lead plaintiffs and co-lead counsel were appointed, and the case was subsequently transferred to the United States District Court for the District of Delaware. On February 3, 2021, the case was consolidated with Harvey v. Kenneth T. McBride, et al (described below). The defendants believe that the case is without merit and intend to defend it vigorously. Due to the early stage of the case, neither the likelihood that a loss, if any, will be realized, nor an estimate of the possible loss or range of loss, if any, can be determined. On August 19, 2019, a purported shareholder derivative suit was filed against us in a case titled City of Cambridge Retirement System v. Kenneth T. McBride, et al , Case No. 2019-0658-AGB, in the Delaware Court of Chancery, alleging breaches of fiduciary duties by officers and/or directors, insider trading, waste of corporate assets, and unjust enrichment. We filed a motion to dismiss in October 2019, and our motion to dismiss was granted in part and denied in part in March 2021. The defendants believe that the case is without merit and intend to defend this case vigorously. Due to the early stage of the case, neither the likelihood that a loss, if any, will be realized, nor an estimate of the possible loss or range of loss, if any, can be determined. On October 3, 2019, a purported shareholder derivative suit was filed against us in a case titled Harvey v. Kenneth T. McBride, et al , Case No. 1:19-cv-01861-CFC, in the United States District Court for the District of Delaware, alleging breaches of fiduciary duties by officers and/or directors, unjust enrichment, waste of corporate assets, and violations of the Securities Exchange Act of 1934. The Court had entered a stipulation to stay the derivative case pending the outcome of the derivative lawsuit pending in the Delaware Court of Chancery. On February 3, 2021, the Court lifted the stay and consolidated the case with In re Stamps.com Stockholder Derivative Litigation (described above), and vacated a prior order appointing lead counsel. The cases are consolidated as In re Stamps.com Stockholder Derivative Litigation , Case No. 1:19-cv-01861-CFC. The defendants believe that the case is without merit and intend to defend this case vigorously. Due to the early stage of the case, neither the likelihood that a loss, if any, will be realized, nor an estimate of the possible loss or range of loss, if any, can be determined. The Company had not accrued any material amounts related to any of the Company’s legal proceedings as of March 31, 2021 or December 31, 2020, respectively. Although management at present believes that the ultimate outcome of the various proceedings, individually and in the aggregate, will not materially harm our financial position, results of operations, cash flows, or overall trends, legal proceedings are subject to inherent uncertainties, and unfavorable rulings or other events could occur. An unfavorable outcome for an amount in excess of management's present expectations may result in a material adverse impact on our business, results of operations, financial position, and overall trends. Commitments Our significant contractual obligations and commercial commitments (other than debt commitments, which are summarized in Note 12 - "Debt" ) consist of operating lease obligations as of March 31, 2021. Please see Note 10 - “Leases” for additional information.

Net Income per Share

Net Income per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Income per Share	Net Income per Share The following table reconciles share amounts utilized to calculate basic and diluted net income per share (in thousands, except per share data): Three Months Ended 2021 2020 Net income $ 34,244 $ 16,494 Basic - weighted average common shares 18,362 17,064 Dilutive effect of common stock equivalents 1,282 1,125 Diluted - weighted average common shares 19,644 18,189 Earnings per share: Basic $ 1.86 $ 0.97 Diluted $ 1.74 $ 0.91 The calculation of dilutive shares excludes the effect of the following options that are considered anti-dilutive (in thousands): Three Months Ended 2021 2020 Anti-dilutive stock options 449 1,527

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation The following table sets forth the stock-based compensation expense that we recognized for the periods indicated (in thousands): Three Months Ended 2021 2020 Stock-based compensation expense relating to: Stock options $ 8,136 $ 10,242 Employee stock purchases 554 483 Total stock-based compensation expense $ 8,690 $ 10,725 Stock-based compensation expense relating to: Cost of revenues $ 921 $ 919 Sales and marketing 2,162 2,307 Research and development 2,990 2,878 General and administrative 2,617 4,621 Total stock-based compensation expense $ 8,690 $ 10,725 The following are the weighted average assumptions used in the Black-Scholes-Merton option valuation model for stock options granted in the periods indicated: Three Months Ended 2021 2020 Expected dividend yield — % — % Risk-free interest rate 0.2 % 1.3 % Expected volatility 89.6 % 82.4 % Expected life (in years) 3.3 3.3

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The following table summarizes goodwill as of December 31, 2020 and March 31, 2021 (in thousands): Stamps.com Segment Metapack Segment Total Goodwill balance at December 31, 2020 $ 241,984 $ 146,769 $ 388,753 Foreign currency translation — 1,600 1,600 Goodwill balance at March 31, 2021 $ 241,984 $ 148,369 $ 390,353 Beginning October 1, 2020, the Stamps.com segment includes operations in Atlanta, Georgia that were previously reported as part of the Metapack segment. All prior periods have been updated to conform to current year presentation of goodwill by segment. We have amortizable and non-amortizable intangible assets consisting of trademarks, trade names, developed technology, non-compete agreements, customer relationships, and other. The gross carrying amount of amortizable and non-amortizable intangible assets was $233.4 million at March 31, 2021 and $232.3 million at December 31, 2020. Non-amortizable assets of $11.4 million as of both March 31, 2021 and December 31, 2020 consist primarily of the trade name relating to the Endicia acquisition. The following table summarizes our amortizable intangible assets as of March 31, 2021 (in thousands, except years): Gross Accumulated Net Carrying Remaining weighted average amortization period (years) Patents and others $ 8,195 $ 8,195 $ — 0.0 Customer relationships 113,934 63,069 50,865 6.7 Technology 83,870 35,295 48,575 8.3 Non-compete 2,211 2,157 54 0.2 Trademarks and trade names 13,808 4,056 9,752 8.2 Total amortizable intangible assets at March 31, 2021 $ 222,018 $ 112,772 $ 109,246 7.4 The following table summarizes our amortizable intangible assets as of December 31, 2020 (in thousands, except years): Gross Accumulated Net Carrying Remaining weighted average amortization period (years) Patents and others $ 8,195 $ 8,195 $ — 0.0 Customer relationships 113,398 59,762 53,636 7.0 Technology 83,427 33,248 50,179 8.5 Non-compete 2,211 2,104 107 0.5 Trademarks and trade names 13,689 3,746 9,943 8.4 Total amortizable intangible assets at December 31, 2020 $ 220,920 $ 107,055 $ 113,865 7.7 We recorded amortization of intangible assets totaling approximately $5.5 million for the three months ended March 31, 2021. We recorded amortization of intangible assets totaling approximately $5.5 million for the three months ended March 31, 2020. Amortization of intangible assets is included in general and administrative expense in the accompanying consolidated statements of operations. Our estimated amortization expense for the next five years and thereafter is as follows (in thousands): Twelve Month Period Ending March 31, Estimated 2022 $ 17,475 2023 10,525 2024 10,082 2025 8,993 2026 7,019 Thereafter 55,152 Total $ 109,246

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesOur income tax expense was $9.9 million for the three months ended March 31, 2021. Our income tax expense was $7.1 million for the three months ended March 31, 2020. Income taxes expected at the US federal statutory income tax rate of 21 percent differ from the reported income tax expense primarily as a result of permanent tax adjustments for non-deductible expenses, state taxes, and tax benefits from research and development tax credits and exercises of stock awards.As of March 31, 2021 and December 31, 2020, we have recorded a valuation allowance of $2.6 million and $2.5 million, respectively, against certain state research and development credits for which we believe it is more likely than not that these deferred tax assets will not be realized.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial assets measured at fair value on a recurring basis are classified in one of the three categories described below: Level 1 - Valuations based on unadjusted quoted prices for identical assets in an active market Level 2 - Valuations based on quoted prices in markets where trading occurs infrequently or whose values are based on quoted prices of instruments with similar attributes in active markets Level 3 - Valuations based on inputs that are unobservable and involve management judgment and our own assumptions about market participants and pricing The following tables summarize our financial assets measured at fair value on a recurring basis as of March 31, 2021 and December 31, 2020 (in thousands): Fair Value Measurement at Reporting Date Using Description March 31, 2021 Quoted Prices in Significant Significant Cash and cash equivalents $ 567,471 $ 567,471 $ — $ — Total $ 567,471 $ 567,471 $ — $ — Fair Value Measurement at Reporting Date Using Description December 31, 2020 Quoted Prices in Significant Significant Cash and cash equivalents $ 443,552 $ 443,552 $ — $ — Total $ 443,552 $ 443,552 $ — $ —

Cash and Cash Equivalents

Cash and Cash Equivalents	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents Our cash equivalents consisted of money market funds at March 31, 2021 and December 31, 2020. We consider all highly liquid investments with an original or remaining maturity of three months or less at the date of purchase to be cash equivalents. At March 31, 2021 and December 31, 2020, we had no material investments. The following tables summarize our cash and cash equivalents as of March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 Cost or Gross Gross Cash and cash equivalents: Cash $ 560,638 $ — $ — $ 560,638 Money market 6,833 — — 6,833 Cash and cash equivalents $ 567,471 $ — $ — $ 567,471 December 31, 2020 Cost or Gross Gross Estimated Cash and cash equivalents: Cash $ 436,720 $ — $ — $ 436,720 Money market 6,832 — — 6,832 Cash and cash equivalents $ 443,552 $ — $ — $ 443,552

Segment Information and Geograp

Segment Information and Geographic Data	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Information and Geographic Data	Segment Information and Geographic Data Segment Information Operating segments are defined as components of an enterprise for which discrete financial information is available that is evaluated regularly by the chief operating decision maker (CODM) for purposes of allocating resources and evaluating financial performance. The Company's Chairman and Chief Executive Officer has been identified as the CODM as defined by guidance regarding segment disclosures. The Company’s reportable segments have been determined based on the distinct nature of their operations and customer bases, and the financial information that is evaluated regularly by the CODM. The Stamps.com segment derives revenue from external customers from offering mailing and multi-carrier shipping labels online and shipping software solutions to consumers, small businesses, e-commerce shippers, enterprise mailers, and high volume shippers. The Stamps.com reportable segment includes the results of brand names Stamps.com, Endicia, ShippingEasy, ShipEngine, ShipStation, and ShipWorks. Stamps.com's customers are primarily located in the US. Beginning October 1, 2020, the Stamps.com segment includes operations in Atlanta, Georgia that were previously reported as part of the Metapack segment. Prior period segment revenues and income (loss) from operations have not been restated as the impact was not material. The Metapack segment consists of the operations of Metapack which derives revenues from external customers from offering multi-carrier enterprise-level shipping software solutions to large e-commerce retailers and brands. Metapack's customers are primarily located in Europe. Revenues, cost of revenues, and operating expenses are generally directly attributed to our segments. Inter-segment revenues are not presented separately, as these amounts are immaterial. Our CODM does not evaluate operating segments using asset information, and therefore total segment assets are not presented. The following table presents our segment information and includes a reconciliation of income from operations to income before income taxes (in thousands): Three Months Ended 2021 2020 Segment revenues Stamps.com $ 172,610 $ 137,545 Metapack 16,480 13,801 Total revenues $ 189,090 $ 151,346 Segment income (loss) from operations Stamps.com $ 44,482 28,227 Metapack (161) (4,056) Total income from operations $ 44,321 $ 24,171 Company's total segment income from operations $ 44,321 $ 24,171 Foreign currency exchange gain (loss), net (89) (138) Interest expense (95) (467) Interest income and other income (loss), net 28 26 Income before income taxes $ 44,165 $ 23,592 Stamps.com segment income from operations included depreciation and amortization expense of $4.7 million and $4.9 million in the three months ended March 31, 2021 and March 31, 2020, respectively. Metapack segment loss from operations included depreciation and amortization expense of $1.7 million and $1.7 million during the three months ended March 31, 2021 and March 31, 2020, respectively. Stamps.com segment income from operations included share-based compensation expense of $7.0 million and $9.0 million in the three months ended March 31, 2021 and March 31, 2020, respectively. Metapack segment loss from operations included share-based compensation expense of $1.7 million and $1.7 million during the three months ended March 31, 2021 and March 31, 2020, respectively. Geographic Data No sales to an individual customer or country other than the US accounted for more than 10% of revenue for the three months ended March 31, 2021 or March 31, 2020. The following table presents our revenues by geography, based on the billing addresses of our customers (in thousands, unaudited): Three Months Ended 2021 2020 Revenues United States $ 170,987 $ 137,070 International 18,103 14,276 Total revenues $ 189,090 $ 151,346

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	Leases The Company's material lease contracts are generally for corporate office space. The Company leases facilities pursuant to noncancelable operating lease agreements expiring through 2032. Operating lease cost for the three months ended March 31, 2021 was approximately $2.6 million. Operating lease cost for the three months ended March 31, 2020 was approximately $1.2 million. The following table is a schedule of maturities of operating lease liabilities as of March 31, 2021 (in thousands): Twelve Month Period Ending March 31, Operating 2022 $ 1,920 2023 9,637 2024 8,809 2025 6,724 2026 7,074 Thereafter 43,848 Total undiscounted cash flows 78,012 Less amount representing interest (18,162) Present value of lease liabilities $ 59,850 The table above reflects payments for noncancelable operating leases with initial or remaining terms of one year or more, net of cash reimbursements for tenant improvements which the Company reasonably expects to receive, as of March 31, 2021. The table above does not include obligations for leases that have not yet commenced and does not include lease payments that were not fixed at commencement or modification. As of March 31, 2021, the weighted-average remaining lease term (in years) and discount rate related to the operating leases were as follows: March 31, 2021 Weighted-average remaining lease term 9.8 Weighted-average discount rate 4.7 %

Accounts Payable and Other Curr

Accounts Payable and Other Current Liabilities	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Accounts Payable and Other Current Liabilities	Accounts Payable and Other Current Liabilities The following table summarizes our accounts payable and other current liabilities as of March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 December 31, 2020 Accounts payable 78,654 $ 69,912 Customer prepayments for postage and shipping labels 93,131 92,852 Income taxes payable 8,782 7,268 Payroll and related accruals 36,175 29,108 Short-term financing obligations 12,435 15,071 Other accruals 1,785 1,756 Accounts payable and other current liabilities $ 230,962 $ 215,967

Debt

Debt	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Debt	Debt During the second quarter of 2020, the Company repaid the existing term loan balance outstanding under the Credit Agreement dated November 18, 2015. The optional prepayment satisfied the $47.5 million term loan balance, gross of debt issuance costs, in full. Revolving Credit Facility On June 29, 2020, we entered into a $130 million revolving credit facility under an amended and restated credit agreement (the “Amended and Restated Credit Agreement”) with a group of banks. Our Amended and Restated Credit Agreement matures on June 29, 2022 (the “Maturity Date”). The Amended and Restated Credit Agreement contains an option, subject to certain conditions, to arrange with existing lenders and/or new lenders to provide up to an aggregate of an additional $75 million in revolving loans. The Amended and Restated Credit Agreement is secured by substantially all of our assets. In connection with entering into the Amended and Restated Credit Agreement, we incurred approximately $762,000 in creditor and third-party fees which were recorded as deferred expense and are being amortized as interest expense over the two year life of the Amended and Restated Credit Agreement. There were no amounts drawn on the revolving credit facility as of March 31, 2021 or December 31, 2020. Because we have a letter of credit outstanding totaling approximately $60,000 relating to a facility lease, we have approximately $129.9 million of available and unused borrowings under the revolving credit facility as of March 31, 2021. Borrowings under the Amended and Restated Credit Agreement are payable on the Maturity Date. The borrowings bear interest, at our option, at the base rate, as defined, plus an applicable margin or at LIBOR plus an applicable margin, in each case such margin will be between 1.25% and 3.00% and is determined by certain financial measures. We will also pay commitment fees on the average daily unused portion of the revolving credit facility, as defined, based upon certain financial measures through the Maturity Date in addition to other fees customary to a credit facility of this size and type. We are subject to certain customary affirmative and negative covenants under our Amended and Restated Credit Agreement, including quarterly financial covenants such as a maximum Consolidated Total Leverage Ratio and a minimum Consolidated Interest Coverage Ratio, as defined therein. As of March 31, 2021, we were in compliance with the covenants of the Amended and Restated Credit Agreement. The Amended and Restated Credit Agreement also includes negative covenants, subject to exceptions, restricting or limiting our ability to among other things, incur additional indebtedness, grant liens, repurchase stock, pay dividends and engage in certain investment, acquisition and disposition transactions. The Amended and Restated Credit Agreement imposes certain requirements in order for us to make any dividend payments. As of March 31, 2021, we were in compliance with these financial covenants. Potential Impact of LIBOR Transition The Chief Executive of the UK Financial Conduct Authority (the “FCA”), which regulates LIBOR, has announced that the FCA will no longer persuade or compel banks to submit rates for the calculation of LIBOR after 2021. That announcement indicates that the continuation of LIBOR on the current basis cannot and will not be guaranteed after 2021. Moreover, it is possible that LIBOR will be discontinued or modified prior to the end of 2021. Under the terms of the Company's Amended and Restated Credit Agreement, in the event of the discontinuance of the LIBOR Rate, a mutually agreed-upon alternate benchmark rate will be established to replace the LIBOR Rate. The Company and the Administrative Agent (as defined in the Amended and Restated Credit Agreement) shall, in good faith, endeavor to establish an alternate benchmark rate that gives due consideration to prevailing market convention for determining a rate of interest for similar credit arrangements in the US at such time. The Company does not anticipate that the discontinuance or modification of the LIBOR Rate will materially impact its liquidity or financial position.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsWe are not aware of any material subsequent events or transactions that have occurred that would require recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation We prepared the consolidated financial statements included herein pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with United States (US) generally accepted accounting principles (GAAP) have been condensed or omitted pursuant to such rules and regulations. We believe that the disclosures are adequate to make the information presented not misleading. We recommend that these consolidated financial statements be read in conjunction with the audited consolidated financial statements and the notes thereto included in our latest annual report on Form 10-K for the fiscal year ended December 31, 2020, filed with the SEC on February 26, 2021. In our opinion, these unaudited consolidated financial statements contain all adjustments (consisting only of normal recurring adjustments) considered necessary to present fairly our financial position as of March 31, 2021, our results of operations for the three months ended March 31, 2021, and our cash flows for the three months ended March 31, 2021. The results of operations for the interim period are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021.
Basis of Consolidation	Basis of Consolidation The consolidated financial statements include all the assets, liabilities, revenues, expenses and cash flows of Stamps.com Inc. and the entities in which we have 100% voting and/or economic control. References in this Report to "we" "us" "our" or "Company" are references to Stamps.com Inc. and its subsidiaries. Intercompany accounts and transactions between consolidated entities have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with US GAAP requires us to make estimates, judgments and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes. Actual results could differ from those estimates, and such differences may be material to the consolidated financial statements. There are significant estimates and judgments inherent in the preparation of the consolidated financial statements including those related to the fair value of intangible assets and goodwill and the allowance for credit losses. The Company considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts on the consolidated financial statements for the period ended March 31, 2021. As events continue to evolve and additional information becomes available, our assumptions and estimates may change materially in future periods.
Accounts Receivable	Accounts Receivable Our accounts receivable relate to mailing and shipping services, postage purchasing and invoicing, branded insurance provided to customers prior to billing, and other receivables. We maintain an allowance for credit losses for expected uncollectible accounts which is recorded as an offset to accounts receivable and changes in such are classified as general and administrative expense in the consolidated statements of operations. We evaluate collectability by reviewing accounts receivable on a collective basis where similar characteristics exist and on an individual basis when we identify specific customers with known collectability issues. The evaluation is based on a combination of factors. If we become aware of a customer’s inability to meet its financial obligations, an allowance is recorded to reduce the net receivable to the amount reasonably believed to be collectible from the customer. Accounts receivable are written off against the allowance for uncollectible accounts when we determine amounts are no longer collectible. We recognize allowances for credit losses for all other customers based on either the age of the receivable or applying a loss rate method which incorporates historical experience and an evaluation of macroeconomic factors, including the estimated impact of COVID-19 on the collectability of our accounts receivable.
Business Combinations	Business Combinations The acquisition method of accounting is used for business combinations. The results of operations of acquired businesses are included in our consolidated financial statements prospectively from the date of acquisition. The fair value of purchase consideration is allocated to the assets acquired and liabilities assumed from the acquired entity and is generally based on their fair value at the acquisition date. The excess of the fair value of purchase consideration over the fair value of the assets acquired and liabilities assumed is recorded as goodwill. Acquisition-related expenses are recognized in our consolidated financial statements as incurred.
Contingencies and Litigation	Contingencies and Litigation In the ordinary course of business, we are subject to various litigation matters as a claimant and a defendant. We record any amounts recovered in these matters when received. We establish loss provisions for claims against us when the loss is both probable and can be reasonably estimated. If either or both of the criteria are not met, we assess whether there is at least a reasonable possibility that a loss, or additional losses, may have been incurred. If there is a reasonable possibility that a loss or additional loss may have been incurred for such proceedings, we disclose the estimate of the amount of loss or possible range of loss, or disclose that an estimate of loss cannot be made, as applicable.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Carrying amounts of certain of our financial instruments, including cash and cash equivalents, accounts receivable and accounts payable, approximate fair value due to their short maturities. When drawn, the Company's outstanding debt held by third party financial institutions is carried at cost, adjusted for debt issuance costs. When drawn, the Company's debt is not publicly traded and the carrying amount typically approximates fair value for debt that accrues interest at a variable rate for companies with similar financial characteristics as the Company, which are considered Level 2 fair value inputs as defined in Note 7 - "Fair Value Measurements" in our consolidated financial statements.
Foreign Currency Translation	Foreign Currency Translation The functional currency of the Company’s major foreign subsidiaries is generally the local currency. Adjustments resulting from translating foreign functional currency financial statements into US dollars are recorded in accumulated other comprehensive income as a component of stockholders’ equity. Foreign currency transaction gains and losses are included in foreign currency exchange gain (loss), net. All assets and liabilities denominated in a foreign currency are translated into US dollars at the exchange rate on the balance sheet date. Revenues and expenses are translated at the average exchange rate during the period.
Goodwill and Indefinite-Lived Intangible Assets	Goodwill and Indefinite-Lived Intangible Assets Goodwill represents the excess of the fair value of consideration given over the fair value of the tangible assets, identifiable intangible assets and liabilities assumed in business combinations. We are required to test goodwill for impairment annually and whenever events or circumstances indicate the fair value of a reporting unit may be below its carrying value. A reporting unit is the operating segment or a business that is one level below that operating segment. Reporting units are aggregated as a single reporting unit if they have similar economic characteristics. Goodwill is reviewed for impairment annually on October 1 utilizing either a qualitative or quantitative assessment. We have an option to make a qualitative assessment of a reporting unit's goodwill for impairment. If we choose to perform a qualitative assessment and determine the fair value more likely than not exceeds the carrying value, no further evaluation is necessary. When we perform a quantitative assessment, we compare the fair value of the reporting unit, which we primarily determine using an income approach based on the present value of discounted cash flows, to the respective carrying value, which includes goodwill. If the fair value of the reporting unit exceeds its carrying value, the goodwill is not considered impaired. If the carrying value is higher than the fair value, the difference is recognized as an impairment loss. As of March 31, 2021, we are not aware of any indicators of impairment that would require an impairment analysis other than our annual goodwill impairment analysis. No instances of impairment to the Company's goodwill were identified during our October 1, 2020 review.
Long-Lived Assets and Finite-Lived Intangible Assets	Long-Lived Assets and Finite-Lived Intangible Assets Long-lived assets including intangible assets with finite useful lives are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. We account for property and equipment at cost less accumulated depreciation and amortization. We compute depreciation using the straight-line method over the estimated useful life of the asset, generally three ten
Income Taxes	Income Taxes We are subject to income taxes in the US and foreign jurisdictions. We provide for income taxes at the current and future enacted tax rate and consistent with the laws applicable in each jurisdiction. We account for income taxes in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic No. 740, Income Taxes ( Income Taxes ), which requires that deferred tax assets and liabilities be recognized using enacted tax rates for the effect of temporary differences between the book and tax basis of recorded assets and liabilities. Income Taxes also requires that deferred tax assets be reduced by a valuation allowance if it is more likely than not that some or all of the net deferred tax assets will not be realized. We record a valuation allowance to reduce our gross deferred tax assets to the amount that is more likely than not (a likelihood of more than 50 percent) to be realized. In order for us to realize our deferred tax assets, we must be able to generate sufficient taxable income. We evaluate the appropriateness of our deferred tax assets and related valuation allowance in accordance with Income Taxes based on all available positive and negative evidence.
Leases	Leases We determine if an arrangement is a lease at inception. Right-of-use (ROU) assets and liabilities are recognized at the present value of the future lease payments at the lease commencement date. For this purpose, we consider only payments that are fixed and determinable at the time of commencement. As most of our leases do not provide an implicit rate, the interest rate used to determine the present value of future lease payments is an estimated incremental borrowing rate. Many of our leases include one or more options to renew. These options are factored into the determination of the lease term and lease payments when their exercise is considered to be reasonably certain. Our lease agreements generally contain lease and non-lease components. Non-lease components primarily include payments for maintenance and utilities. We elected the practical expedient to combine fixed payments for non-lease components with our lease payments and account for them together as a single lease component which increases the amount of the ROU assets and liabilities. We also elected to recognize the associated lease payments for leases with an initial term of 12 months or less in the consolidated statements of operations on a straight-line basis without recognizing a ROU asset or liability. Operating leases are included in lease right-of-use assets, current portion of lease right-of-use liabilities, and long-term portion of lease right-of-use liabilities on our consolidated balance sheets. Operating lease expense is recognized on a straight-line basis over the lease term in income from operations on our consolidated statements of operations.
Other Current Assets	Other Current AssetsOther current assets principally consist of prepayments for postage and shipping labels and inventory.
Other Liabilities	Other Liabilities Other liabilities principally consist of long-term unrecognized income tax benefits, as well as indirect tax liabilities and other liabilities.
Revenue Recognition	Deferred RevenueOur deferred revenue relates mainly to service revenue, which generally arises due to the timing of payment versus the provision of services for certain customers billed in advance. Revenue Recognition We recognize revenues when we transfer control of promised goods or services to our customers in an amount that reflects the consideration to which we expect to be entitled to in exchange for those goods or services. We account for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance, and collectability of consideration is probable. Our payment terms vary by the products and services offered. The term between billings and when payment is due is not significant. Revenues are presented on a disaggregated basis on the consolidated statements of operations. Service revenue is recognized over time for each month that customers have access to our platform or at a point in time when assets are transferred to the customer. We earn service revenue from our mailing and shipping operations in several different ways: (1) customers may pay us a monthly fee, based on a subscription plan which may be waived or refunded for certain customers, for which we provide them access to our platform, in which case revenue is earned over the period of time that the customers have access to the platform which is typically month-to-month; (2) we may be compensated directly by our carriers for shipping labels printed that meet certain requirements, in which case revenue is earned over time, which is typically in the same month that the relevant labels are printed; (3) we may earn revenue from customers when they purchase postage, print shipping labels or perform other transactions using our solutions, in which case revenue is earned at the point in time we transfer an asset to the customer and have a present right of payment for the asset transferred; (4) we may earn revenue that may take the form of some or all of the spread between the rate a customer pays and the rate the carrier or integration partner receives, either charged directly or paid by our partners, in which case revenue is earned at a point in time, which is typically when the customer purchases postage or prints a shipping label; and (5) we may earn other types of revenue shares or other compensation from specific customers that have access to our platform or through integration partners, in which case revenue is recognized at a point in time, which is when we have fulfilled our performance obligations. In the case of monthly fees based on subscription plans, the Company recognizes a reduction of revenue in the period for which a waiver is granted or when a refund is processed, which is typically the same period in which the associated subscription revenue is recognized or, in the case of refunds, could be a later period. Waivers and refunds were not material to the consolidated financial statements during the three months ended March 31, 2021 or March 31, 2020, respectively. Customers may purchase delivery services from carriers through our mailing and shipping solutions. When funds are transferred directly from customers to the carrier, these funds are not recognized as revenue. We also provide mailing and shipping services for which the cost of postage or delivery is included in the cost of the service and, therefore, is recognized as service revenue. Product revenue consists of products sold through the mailing and shipping supplies stores which are available to our customers from within some of our mailing and shipping solutions. Products sold include mailing labels, shipping labels, thermal printers, scales, and other mailing and shipping-focused office supplies. We recognize product revenue on product purchases upon shipment of orders to customers. We provide our customers with the opportunity to purchase parcel insurance directly through our solutions. Insurance revenue represents the amount we receive from customers net of the costs paid to our insurance providers. We recognize insurance revenue on insurance purchases upon the ship date of the insured package, which is the point in time when we have fulfilled our performance obligations. Customized postage revenue, which includes the face value of postage, from the sale of customized postage sheets and rolls is recognized upon transfer of control of the product to the customer, which occurs upon our delivery to the carrier. In the second quarter of 2020, we received notification from the US Postal Service (USPS) that it was eliminating its customized postage program and also revoking our authorization to offer products pursuant to that program effective June 16, 2020. As a result, we do not expect material customized postage revenue or cost of revenue after June 2020.
Segment Information	Segment InformationOur operations consist of two segments: Stamps.com and Metapack.
Short-Term Financing Obligations	Short-Term Financing Obligations We utilize short-term financing, which is separate from our debt as described in Note 12 - "Debt,"
Stock-Based Compensation	Stock-Based Compensation We account for share-based employee compensation plans under the fair value recognition and measurement provisions in accordance with applicable accounting standards, which require all share-based payments to employees, including grants of stock options and restricted stock units (RSUs), to be measured based on the grant date fair value of the awards, with the resulting expense generally recognized on a straight-line basis over the period during which the employee is required to perform service in exchange for the award. We account for forfeitures as they occur. We use the Black-Scholes-Merton option valuation model to estimate the fair value of share-based payment awards on the date of grant, which requires us to use a number of estimates and subjective assumptions, including stock price volatility, expected term, and risk-free interest rates. In the case of options we grant, our assumption of expected volatility is based on the historical volatility of our stock price over the term equal to the expected life of the options. We base the risk-free interest rate on US Treasury zero-coupon issues with a remaining term equal to the expected life of the options assumed at the date of grant. The estimated expected life represents the weighted average period the stock options are expected to remain outstanding, determined based on an analysis of historical exercise behavior.
Trademarks, Trade Names, and Other Intangible Assets (excluding Goodwill)	Trademarks, Trade Names, and Other Intangible Assets (excluding Goodwill) Acquired trademarks, trade names, and other intangibles (excluding goodwill) include both amortizable and non-amortizable assets and are included in intangible assets, net in the accompanying consolidated balance sheets. Intangible assets are carried at cost less accumulated amortization. Cost associated with internally developed intangible assets is typically expensed as incurred as research and development costs. Amortization of amortizable intangible assets is calculated on a straight-line basis, which is consistent with the expected future cash flows.
Accounting Guidance Adopted in 2021 and Guidance Not Yet Adopted	Accounting Guidance Adopted in 2021 Income Taxes In December 2019, the FASB issued ASU 2019-12, a standard which eliminates certain exceptions to the general principles of ASC Topic 740 Income Taxes . The guidance became effective for the Company on January 1, 2021. The adoption of the guidance did not have a material impact on the Company's consolidated financial statements. Accounting Guidance Not Yet Adopted Reference Rate Reform In March 2020, the FASB issued 2020-04, optional accounting guidance for a limited period of time to ease the potential burden in accounting for reference rate reform. The new standard provides expedients and exceptions to existing accounting requirements for contract modifications and hedge accounting related to transitioning from discontinued reference rates, such as the London Interbank Offered Rate (LIBOR), to alternative reference rates, if certain criteria are met. The new standard was effective upon issuance and generally can be applied to applicable contract modifications through December 31, 2022. We are currently evaluating the impact of the transition from LIBOR to alternative reference interest rates on our Amended and Restated Credit Agreement, as described in Note 12 - " Debt ", but do not expect a significant impact to our operating results, financial position or cash flows.

Net Income per Share (Tables)

Net Income per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Calculation of Basic and Diluted Net Income Per Share	The following table reconciles share amounts utilized to calculate basic and diluted net income per share (in thousands, except per share data): Three Months Ended 2021 2020 Net income $ 34,244 $ 16,494 Basic - weighted average common shares 18,362 17,064 Dilutive effect of common stock equivalents 1,282 1,125 Diluted - weighted average common shares 19,644 18,189 Earnings per share: Basic $ 1.86 $ 0.97 Diluted $ 1.74 $ 0.91
Anti-dilutive Securities Excluded from Computation of Earnings Per Share	The calculation of dilutive shares excludes the effect of the following options that are considered anti-dilutive (in thousands): Three Months Ended 2021 2020 Anti-dilutive stock options 449 1,527

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Expense	The following table sets forth the stock-based compensation expense that we recognized for the periods indicated (in thousands): Three Months Ended 2021 2020 Stock-based compensation expense relating to: Stock options $ 8,136 $ 10,242 Employee stock purchases 554 483 Total stock-based compensation expense $ 8,690 $ 10,725 Stock-based compensation expense relating to: Cost of revenues $ 921 $ 919 Sales and marketing 2,162 2,307 Research and development 2,990 2,878 General and administrative 2,617 4,621 Total stock-based compensation expense $ 8,690 $ 10,725
Weighted Average Assumptions Used in Black-Scholes-Merton Option Valuation Model	The following are the weighted average assumptions used in the Black-Scholes-Merton option valuation model for stock options granted in the periods indicated: Three Months Ended 2021 2020 Expected dividend yield — % — % Risk-free interest rate 0.2 % 1.3 % Expected volatility 89.6 % 82.4 % Expected life (in years) 3.3 3.3

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table summarizes goodwill as of December 31, 2020 and March 31, 2021 (in thousands): Stamps.com Segment Metapack Segment Total Goodwill balance at December 31, 2020 $ 241,984 $ 146,769 $ 388,753 Foreign currency translation — 1,600 1,600 Goodwill balance at March 31, 2021 $ 241,984 $ 148,369 $ 390,353
Schedule of Acquired Intangible Assets	The following table summarizes our amortizable intangible assets as of March 31, 2021 (in thousands, except years): Gross Accumulated Net Carrying Remaining weighted average amortization period (years) Patents and others $ 8,195 $ 8,195 $ — 0.0 Customer relationships 113,934 63,069 50,865 6.7 Technology 83,870 35,295 48,575 8.3 Non-compete 2,211 2,157 54 0.2 Trademarks and trade names 13,808 4,056 9,752 8.2 Total amortizable intangible assets at March 31, 2021 $ 222,018 $ 112,772 $ 109,246 7.4 The following table summarizes our amortizable intangible assets as of December 31, 2020 (in thousands, except years): Gross Accumulated Net Carrying Remaining weighted average amortization period (years) Patents and others $ 8,195 $ 8,195 $ — 0.0 Customer relationships 113,398 59,762 53,636 7.0 Technology 83,427 33,248 50,179 8.5 Non-compete 2,211 2,104 107 0.5 Trademarks and trade names 13,689 3,746 9,943 8.4 Total amortizable intangible assets at December 31, 2020 $ 220,920 $ 107,055 $ 113,865 7.7
Schedule of Future Amortization Expense	Our estimated amortization expense for the next five years and thereafter is as follows (in thousands): Twelve Month Period Ending March 31, Estimated 2022 $ 17,475 2023 10,525 2024 10,082 2025 8,993 2026 7,019 Thereafter 55,152 Total $ 109,246

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Financial Assets Measured at Fair Value on a Recurring Basis	The following tables summarize our financial assets measured at fair value on a recurring basis as of March 31, 2021 and December 31, 2020 (in thousands): Fair Value Measurement at Reporting Date Using Description March 31, 2021 Quoted Prices in Significant Significant Cash and cash equivalents $ 567,471 $ 567,471 $ — $ — Total $ 567,471 $ 567,471 $ — $ — Fair Value Measurement at Reporting Date Using Description December 31, 2020 Quoted Prices in Significant Significant Cash and cash equivalents $ 443,552 $ 443,552 $ — $ — Total $ 443,552 $ 443,552 $ — $ —

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Summary of Cash and Cash Equivalents	The following tables summarize our cash and cash equivalents as of March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 Cost or Gross Gross Cash and cash equivalents: Cash $ 560,638 $ — $ — $ 560,638 Money market 6,833 — — 6,833 Cash and cash equivalents $ 567,471 $ — $ — $ 567,471 December 31, 2020 Cost or Gross Gross Estimated Cash and cash equivalents: Cash $ 436,720 $ — $ — $ 436,720 Money market 6,832 — — 6,832 Cash and cash equivalents $ 443,552 $ — $ — $ 443,552

Segment Information and Geogr_2

Segment Information and Geographic Data (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following table presents our segment information and includes a reconciliation of income from operations to income before income taxes (in thousands): Three Months Ended 2021 2020 Segment revenues Stamps.com $ 172,610 $ 137,545 Metapack 16,480 13,801 Total revenues $ 189,090 $ 151,346 Segment income (loss) from operations Stamps.com $ 44,482 28,227 Metapack (161) (4,056) Total income from operations $ 44,321 $ 24,171 Company's total segment income from operations $ 44,321 $ 24,171 Foreign currency exchange gain (loss), net (89) (138) Interest expense (95) (467) Interest income and other income (loss), net 28 26 Income before income taxes $ 44,165 $ 23,592
Revenue from External Customers by Geographic Areas	The following table presents our revenues by geography, based on the billing addresses of our customers (in thousands, unaudited): Three Months Ended 2021 2020 Revenues United States $ 170,987 $ 137,070 International 18,103 14,276 Total revenues $ 189,090 $ 151,346

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity	The following table is a schedule of maturities of operating lease liabilities as of March 31, 2021 (in thousands): Twelve Month Period Ending March 31, Operating 2022 $ 1,920 2023 9,637 2024 8,809 2025 6,724 2026 7,074 Thereafter 43,848 Total undiscounted cash flows 78,012 Less amount representing interest (18,162) Present value of lease liabilities $ 59,850
Lessee, Operating Lease, Liability, Term And Discount Rate	As of March 31, 2021, the weighted-average remaining lease term (in years) and discount rate related to the operating leases were as follows: March 31, 2021 Weighted-average remaining lease term 9.8 Weighted-average discount rate 4.7 %

Accounts Payable and Other Cu_2

Accounts Payable and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	The following table summarizes our accounts payable and other current liabilities as of March 31, 2021 and December 31, 2020 (in thousands): March 31, 2021 December 31, 2020 Accounts payable 78,654 $ 69,912 Customer prepayments for postage and shipping labels 93,131 92,852 Income taxes payable 8,782 7,268 Payroll and related accruals 36,175 29,108 Short-term financing obligations 12,435 15,071 Other accruals 1,785 1,756 Accounts payable and other current liabilities $ 230,962 $ 215,967

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Allowance for credit losses	$ 9.1	$ 11.9

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Deferred Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounting Policies [Abstract]
Deferred revenue recognized in the period	$ 5.9	$ 6.4

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Property, Plant and Equipment (Details)	3 Months Ended
	Mar. 31, 2021
Furniture, Fixtures and Equipment | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful life	3 years
Furniture, Fixtures and Equipment | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful life	5 years
Building and Building Improvements | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful life	10 years
Building and Building Improvements | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful life	40 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Other Current Assets (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Prepayments for postage and shipping labels	$ 64.5	$ 82.4

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Segment Information (Details)	3 Months Ended
	Mar. 31, 2021segment
Accounting Policies [Abstract]
Number of reportable segments	2

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Short Term Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Short-term financing obligation	$ 12,435	$ 15,071
Unused credit	$ 57,600	$ 57,000

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Treasury Stock (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounting Policies [Abstract]
Treasury stock, shares, acquired (in shares)	136	80
Treasury stock, value, acquired, cost method	$ 27,031	$ 8,577

Commitments and Contingencies (

Commitments and Contingencies (Details)	May 19, 2019claim	Mar. 13, 2019claim	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual | $			$ 0	$ 0
Karinski v. Stamps.com, Inc. et al, Case 2:19-cv-01828 | Pending Litigation
Loss Contingencies [Line Items]
Number of complaints or suits filed		2
Putative Class Action Complaint
Loss Contingencies [Line Items]
Number of claims dismissed		1
In Re Stamps.com Stockholder Derivative Litigation, Case 2:19-cv-04272 | Pending Litigation
Loss Contingencies [Line Items]
Number of complaints or suits filed	2

Net Income per Share (Details)

Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 34,244	$ 16,494
Basic - weighted average common shares (in shares)	18,362	17,064
Dilutive effect of common stock equivalents (in shares)	1,282	1,125
Diluted - weighted average common shares (in shares)	19,644	18,189
Earnings per share:
Basic (in dollars per share)	$ 1.86	$ 0.97
Diluted (in dollars per share)	$ 1.74	$ 0.91
Employee stock option
Antidilutive Securities Excluded from Computation of Diluted Shares [Line Items]
Anti-dilutive stock options (in shares)	449	1,527

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 8,690	$ 10,725
Weighted Average Assumptions used in Black-Scholes-Merton Option Valuation Model [Abstract]
Expected dividend yield	0.00%	0.00%
Risk-free interest rate	0.20%	1.30%
Expected volatility	89.60%	82.40%
Expected life (in years)	3 years 3 months 18 days	3 years 3 months 18 days
Cost of revenues
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 921	$ 919
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	2,162	2,307
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	2,990	2,878
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	2,617	4,621
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	8,136	10,242
Employee stock purchases
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 554	$ 483

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Goodwill [Roll Forward]
Goodwill	$ 388,753
Foreign currency translation	1,600
Goodwill	390,353
Stamps.com
Goodwill [Roll Forward]
Goodwill	241,984
Foreign currency translation	0
Goodwill	241,984
MetaPack
Goodwill [Roll Forward]
Goodwill	146,769
Foreign currency translation	1,600
Goodwill	$ 148,369

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Goodwill and Intangible Assets [Line Items]
Amortizable and non-amortizable intangible assets gross carrying amount	$ 233,400		$ 232,300
Non-amortizable assets	11,400		11,400
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	222,018		220,920
Accumulated  Amortization	112,772		107,055
Net Carrying Amount	$ 109,246		$ 113,865
Remaining weighted average amortization period (years)	7 years 4 months 24 days		7 years 8 months 12 days
Amortization of intangible assets	$ 5,500	$ 5,500
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2022	17,475
2023	10,525
2024	10,082
2025	8,993
2026	7,019
Thereafter	55,152
Net Carrying Amount	109,246		$ 113,865
Patents and others
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	8,195		8,195
Accumulated  Amortization	8,195		8,195
Net Carrying Amount	$ 0		0
Remaining weighted average amortization period (years)	0 years
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 0		0
Customer relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	113,934		113,398
Accumulated  Amortization	63,069		59,762
Net Carrying Amount	$ 50,865		$ 53,636
Remaining weighted average amortization period (years)	6 years 8 months 12 days		7 years
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 50,865		$ 53,636
Technology
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	83,870		83,427
Accumulated  Amortization	35,295		33,248
Net Carrying Amount	$ 48,575		$ 50,179
Remaining weighted average amortization period (years)	8 years 3 months 18 days		8 years 6 months
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 48,575		$ 50,179
Non-compete
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	2,211		2,211
Accumulated  Amortization	2,157		2,104
Net Carrying Amount	$ 54		$ 107
Remaining weighted average amortization period (years)	2 months 12 days		6 months
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 54		$ 107
Trademarks and trade names
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying  Amount	13,808		13,689
Accumulated  Amortization	4,056		3,746
Net Carrying Amount	$ 9,752		$ 9,943
Remaining weighted average amortization period (years)	8 years 2 months 12 days		8 years 4 months 24 days
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Net Carrying Amount	$ 9,752		$ 9,943

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Tax Credit Carryforward [Line Items]
Income tax expense	$ 9,921	$ 7,098
State and Local Jurisdiction | Research Tax Credit Carryforward
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 2,600		$ 2,500

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 567,471	$ 443,552
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	567,471	443,552
Total	567,471	443,552
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets  for Identical  Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	567,471	443,552
Total	567,471	443,552
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total	0	0
Fair Value, Measurements, Recurring | Significant Unobservable  Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total	$ 0	$ 0

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and cash equivalents [Abstract]
Cost or Amortized Cost	$ 567,471	$ 443,552
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	567,471	443,552
Cash
Cash and cash equivalents [Abstract]
Cost or Amortized Cost	560,638	436,720
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	560,638	436,720
Money market
Cash and cash equivalents [Abstract]
Cost or Amortized Cost	6,833	6,832
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 6,833	$ 6,832

Segment Information and Geogr_3

Segment Information and Geographic Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 189,090	$ 151,346
Income from operations	44,321	24,171
Foreign currency exchange gain (loss), net	(89)	(138)
Interest expense	(95)	(467)
Interest income and other income (loss), net	28	26
Income before income taxes	44,165	23,592
Depreciation and amortization	6,443	6,588
Stock-based compensation expense	8,690	10,725
Stamps.com
Segment Reporting Information [Line Items]
Revenues	172,610	137,545
Income from operations	44,482	28,227
Depreciation and amortization	4,700	4,900
Stock-based compensation expense	7,000	9,000
MetaPack
Segment Reporting Information [Line Items]
Revenues	16,480	13,801
Income from operations	(161)	(4,056)
Depreciation and amortization	1,700	1,700
Stock-based compensation expense	$ 1,700	$ 1,700

Segment Information and Geogr_4

Segment Information and Geographic Data - Schedule of Revenue by Geographical Data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 189,090	$ 151,346
United States
Segment Reporting Information [Line Items]
Revenues	170,987	137,070
International
Segment Reporting Information [Line Items]
Revenues	$ 18,103	$ 14,276

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating lease cost	$ 2,600	$ 1,200
2022	1,920
2023	9,637
2024	8,809
2025	6,724
2026	7,074
Thereafter	43,848
Total undiscounted cash flows	78,012
Less amount representing interest	(18,162)
Present value of lease liabilities	$ 59,850
Weighted-average remaining lease term	9 years 9 months 18 days
Weighted-average discount rate	4.70%

Accounts Payable and Other Cu_3

Accounts Payable and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accounts payable	$ 78,654	$ 69,912
Customer prepayments for postage and shipping labels	93,131	92,852
Income taxes payable	8,782	7,268
Payroll and related accruals	36,175	29,108
Short-term financing obligations	12,435	15,071
Other accruals	1,785	1,756
Accounts payable and other current liabilities	$ 230,962	$ 215,967

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	Jun. 29, 2020	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2020
Line of Credit Facility [Line Items]
Repayments of debt		$ 0		$ 3,093,000
Term Loan
Line of Credit Facility [Line Items]
Repayments of debt			$ 47,500,000
Letter of Credit
Line of Credit Facility [Line Items]
Total debt		60,000
Amended Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 130,000,000
Additional borrowing capacity	75,000,000
Debt issuance costs	$ 762,000
Debt issuance costs, amortization period	2 years
Draws on revolving credit facility		0			$ 0
Unused borrowing capacity		$ 129,900,000
Amended Credit Agreement | Revolving Credit Facility | London Interbank Offered Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (percent)		1.25%
Amended Credit Agreement | Revolving Credit Facility | London Interbank Offered Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate (percent)		3.00%