MarketAxess (MKTX) 10-K 19 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 16, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	MKTX
Entity Registrant Name	MARKETAXESS HOLDINGS INC.
Entity Central Index Key	0001278021
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
ICFR Auditor Attestation Flag	true
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		37,995,877
Entity Public Float			$ 16.3
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.003 par value
Security Exchange Name	NASDAQ
Entity File Number	001-34091
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	52-2230784
Entity Address, Address Line One	55 Hudson Yards
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10001
Document Annual Report	true
Document Transition Report	false
City Area Code	212
Local Phone Number	813-6000
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for the 2021 Annual Meeting of Stockholders are incorporated by reference into Items 10, 11, 12, 13 and 14 of Part III of this Form 10-K.

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash and cash equivalents	$ 460,858	$ 270,124
Cash segregated under federal regulations	50,059
Investments, at fair value	28,111	230,477
Accounts receivable, net of allowance of $163 and $57 as of December 31, 2020 and 2019, respectively	79,577	62,017
Receivables from broker-dealers, clearing organizations and customers	279,915
Goodwill	147,388	146,861
Intangible assets, net of accumulated amortization	95,354	60,986
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	85,204	71,795
Operating lease right-of-use assets	75,924	81,399
Prepaid expenses and other assets	29,039	31,271
Total assets	1,331,429	954,930
Liabilities
Accrued employee compensation	62,326	47,365
Payables to broker-dealers, clearing organizations and customers	133,326
Income and other tax liabilities	42,750	16,690
Accounts payable, accrued expenses and other liabilities	44,354	22,793
Operating lease liabilities	93,612	97,991
Total liabilities	376,368	184,839
Commitments and Contingencies (Note 15)
Stockholders' equity
Preferred stock
Common stock	123	122
Additional paid-in capital	329,742	342,541
Treasury stock - Common stock voting, at cost, 2,845,770 and 2,810,609 shares as of December 31, 2020 and 2019, respectively	(169,523)	(153,388)
Retained earnings	799,369	591,086
Accumulated other comprehensive loss	(4,650)	(10,270)
Total stockholders' equity	955,061	770,091
Total liabilities and stockholders' equity	1,331,429	954,930
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Allowance for accounts receivable	$ 163	$ 57
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	4,855,000	4,855,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.003	$ 0.003
Common stock, shares authorized	110,000,000	110,000,000
Common stock, shares issued	40,851,100	40,746,593
Common stock, shares outstanding	38,005,330	37,935,984
Treasury stock, shares	2,845,770	2,810,609
Series A Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	110,000	110,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock Non-Voting [Member]
Common stock, par value	$ 0.003	$ 0.003
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Revenues	$ 689,125	$ 511,352	$ 435,565
Expenses
Employee compensation and benefits	156,885	131,079	109,117
Depreciation and amortization	35,996	26,857	23,080
Technology and communications	34,092	26,792	23,866
Professional and consulting fees	32,304	25,534	21,521
Occupancy	13,425	11,639	14,176
Marketing and advertising	7,940	11,559	12,114
Clearing costs	21,058	11,314	7,754
General and administrative	12,697	15,696	11,353
Total expenses	314,397	260,470	222,981
Operating income	374,728	250,882	212,584
Other income (expense)
Investment income	2,446	8,063	6,112
Interest expense	(1,142)
Other, net	(1,673)	(1,521)	(610)
Total other income (expense)	(369)	6,542	5,502
Income before income taxes	374,359	257,424	218,086
Provision for income taxes	74,982	52,522	45,234
Net income	$ 299,377	$ 204,902	$ 172,852
Net income per common share
Basic	$ 8.01	$ 5.53	$ 4.68
Diluted	7.85	5.40	4.57
Cash dividends declared per common share	$ 2.40	$ 2.04	$ 1.68
Weighted average shares outstanding
Basic	37,359	37,083	36,958
Diluted	38,144	37,956	37,855
Commissions [Member]
Revenues
Revenues	$ 634,445	$ 463,856	$ 390,834
Information Services [Member]
Revenues
Revenues	34,341	30,730	28,227
Post-trade Services [Member]
Revenues
Revenues	19,460	15,763	15,346
Other [Member]
Revenues
Revenues	$ 879	$ 1,003	$ 1,158

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 299,377	$ 204,902	$ 172,852
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(1,468), $(1,218) and $1,290, respectively	6,164	1,128	(2,078)
Net unrealized gain (loss) on securities available-for-sale, net of tax of $(172), $312, and $(23), respectively	(544)	996	(90)
Comprehensive income	$ 304,997	$ 207,026	$ 170,684

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency exchange hedge, tax expense (benefit)	$ (1,468)	$ (1,218)	$ 1,290
Securities available-for-sale, tax expense (benefit)	$ (172)	$ 312	$ (23)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock Voting [Member]	Additional Paid-In Capital [Member]	Treasury Stock - Common Stock Voting [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2017	$ 514,768	$ 121	$ 331,081	$ (159,791)	$ 353,583	$ (10,226)
Net income	172,852				172,852
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(2,078)					(2,078)
Unrealized net (loss) on securities available-for-sale, net of tax	(90)					(90)
Stock-based compensation	15,850		15,850
Exercise of stock options	2,973	1	2,972
Withholding tax payments on restricted stock vesting and stock option exercises	(8,043)		(8,043)
Repurchases of common stock	(25,171)			(25,171)
Cash dividend on common stock	(63,183)				(63,183)
Ending Balance at Dec. 31, 2018	607,878	122	341,860	(184,962)	463,252	(12,394)
Net income	204,902				204,902
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	1,128					1,128
Unrealized net (loss) on securities available-for-sale, net of tax	996					996
Stock-based compensation	25,294		25,294
Exercise of stock options	1,207		1,207
Withholding tax payments on restricted stock vesting and stock option exercises	(25,820)		(25,820)
Treasury shares used for acquisition	48,830			48,830
Repurchases of common stock	(17,256)			(17,256)
Cash dividend on common stock	(77,068)				(77,068)
Ending Balance at Dec. 31, 2019	770,091	122	342,541	(153,388)	591,086	(10,270)
Net income	299,377				299,377
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	6,164					6,164
Unrealized net (loss) on securities available-for-sale, net of tax	(544)					(544)
Stock-based compensation	25,613		25,613
Exercise of stock options	4,007	1	4,006
Withholding tax payments on restricted stock vesting and stock option exercises	(42,418)		(42,418)
Repurchases of common stock	(16,135)			(16,135)
Cash dividend on common stock	(91,094)				(91,094)
Ending Balance at Dec. 31, 2020	$ 955,061	$ 123	$ 329,742	$ (169,523)	$ 799,369	$ (4,650)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Stockholders Equity [Abstract]
Cash dividends declared per common share	$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 2.40	$ 2.04	$ 1.68

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 299,377	$ 204,902
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35,996	26,857
Amortization of operating lease right-of-use assets	6,842	5,795
Stock-based compensation expense	25,613	25,294
Deferred taxes	10,099	2,674
Other	(550)	(778)
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(18,015)	(2,962)
(Increase) in receivables from broker-dealers, clearing organizations and customers	(182,871)
(Increase) in prepaid expenses and other assets	(1,977)	(4,624)
Decrease (Increase) in trading securities	67,952	4,045
Increase in accrued employee compensation	14,961	8,312
Increase in payables to broker-dealers, clearing organizations and customers	133,326
Increase in income and other tax liabilities	16,189	187
Increase (decrease) in accounts payable, accrued expenses and other liabilities	6,006	(820)
(Decrease) in operating lease liabilities	(5,788)	(829)
Net cash provided by operating activities	404,489	265,935
Cash flows from investing activities
Acquisitions, net of cash and cash equivalents acquired	(23,297)	(97,430)
Proceeds from maturities and sales, available-for-sale investments	170,657	170,936
Purchases, available-for-sale investments	(32,865)	(160,827)
Purchases of furniture, equipment and leasehold improvements	(15,010)	(12,292)
Capitalization of software development costs	(30,618)	(22,408)
Other		(30)
Net cash provided by (used in) investing activities	68,867	(122,051)
Cash flows from financing activities
Cash dividend on common stock	(90,566)	(76,231)
Exercise of stock options	4,007	1,207
Withholding tax payments on restricted stock vesting and stock option exercises	(42,418)	(25,820)
Repurchases of common stock	(16,135)	(17,256)
Proceeds from short-term borrowings	578,356
Repayments of short-term borrowings	(578,356)
Net cash (used in) financing activities	(145,112)	(118,100)
Effect of exchange rate changes on cash and cash equivalents	5,553	1,011
Cash and cash equivalents including restricted cash
Net increase for the period	333,797	26,795
Beginning of period	274,253	247,458
End of period	608,050	274,253
Supplemental cash flow information:
Cash paid for income taxes	45,046	51,766
Cash paid for interest	1,142
Right-of-use assets obtained in exchange for operating lease liabilities	727	7,464
Non-cash investing and financing activity:
Exercise of stock options - cashless	10,866	1,811
Intangible assets acquired in exchange for contingent consideration payable	14,665
Liabilities assumed in connection with acquisition:
Fair value of assets acquired		148,425
Cash paid for acquisition of business, net of cash and cash equivalents acquired		(97,430)
Treasury stock used for acquisition of business		(48,830)
Liabilities assumed		2,165
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease (Increase) in trading securities	$ (2,671)	$ (2,118)

Organization and Principal Busi

Organization and Principal Business Activity	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Organization and Principal Business Activity	1. Organization and Principal Business Activity MarketAxess Holdings Inc. (the “Company” or “MarketAxess”) was incorporated in the State of Delaware on April 11, 2000. Through its subsidiaries, MarketAxess operates leading electronic trading platforms delivering expanded liquidity opportunities, improved execution quality and significant cost savings across global fixed-income markets. Over 1,800 institutional investor and broker-dealer firms are active users of MarketAxess’ patented trading technology, accessing global liquidity on its platforms in U.S. investment-grade bonds, U.S. high-yield bonds, U.S. Treasuries, emerging market debt, Eurobonds and other fixed income securities. Through its Open Trading TM TM

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated. Certain reclassifications have been made to the prior periods’ consolidated financial statements in order to conform to the current period presentation. Such reclassifications are immaterial, individually and in the aggregate, to both current and all previously issued financial statements taken as a whole and have no effect on previously reported net income. Accounting Pronouncements, Recently Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15, “Intangibles—Goodwill and Other—Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract” (“ASU 2018-15”). The standard requires the capitalization of implementation costs incurred in a cloud computing arrangement to be aligned with the requirements for capitalizing costs incurred to develop or obtain internal-use software. The Company adopted ASU 2018-15 effective July 1, 2019 on a prospective basis. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In January 2017, the FASB issued ASU 2017-04, “Intangibles-Goodwill and Other” (“ASU 2017-04”). ASU 2017-04 simplifies the testing for goodwill impairment, which eliminates the requirement to determine the fair value of individual assets and liabilities of a reporting unit to measure goodwill impairment. Instead, goodwill impairment testing will be performed by comparing the fair value of the reporting unit with its carrying amount and recognizing impairment by which the carrying amount exceeds the reporting unit’s fair value. The Company adopted ASU 2017-04 effective January 1, 2020 on a prospective basis. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In June 2016, the FASB issued ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326) -Measurement of Credit Losses on Financial Instruments”. This ASU amends several aspects of the measurement of credit losses on financial instruments, including replacing the existing incurred credit loss model and other models with the Current Expected Credit Losses model (“CECL”). Under CECL, the allowance for losses for financial assets that are measured at amortized cost reflects management’s estimate of credit losses over the remaining expected life of the financial assets. Expected credit losses for newly recognized financial assets, as well as changes to expected credit losses during the period, would be recognized in earnings. Expected credit losses will be measured based on historical experience, current conditions and forecasts that affect the collectability of the reported amount. The Company adopted this ASU on January 1, 2020 using the modified retrospective method of adoption. Adoption of this ASU did not have a material impact on the Company's Consolidated Financial Statements. Accounting Pronouncements, Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting”, which is designed to ease the potential burden in accounting for the transition away from LIBOR. The ASU applies to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued and replaced with alternative reference rates as a result of reference rate reform. The ASU provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The ASU was effective for all entities as of March 12, 2020 and can be adopted from this date through December 31, 2022. The Company does not expect adoption of this ASU to have a material impact on its Consolidated F inancial S tatements. Cash and Cash Equivalents The Company defines cash equivalents as short-term interest-bearing investments with maturities at the time of purchase of three months or less. Investments The Company determines the appropriate classification of securities at the time of purchase which are recorded in the Consolidated Statements of Financial Condition on the trade date. Securities are classified as available-for-sale or trading. The Company’s available-for-sale investments are comprised of investment-grade corporate debt securities. Available-for-sale investments are carried at fair value with the unrealized gains or losses reported in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Trading investments include investment-grade corporate debt securities and U.S. Treasuries and are carried at fair value, with realized and unrealized gains or losses included in other, net in the Consolidated Statements of Operations. The Company assesses whether an other-than-temporary impairment loss on the available-for-sale investments has occurred due to declines in fair value or other market conditions. The portion of an other-than-temporary impairment related to credit loss is recorded as a charge in the Consolidated Statements of Operations. The remainder is recognized in accumulated other comprehensive loss if the Company does not intend to sell the security and it is more likely than not that the Company will not be required to sell the security prior to recovery. No charges for other-than-temporary losses were recorded during the years ended December 31, 2020, 2019 and 2018. Fair Value Financial Instruments Fair value is defined as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” A three-tiered hierarchy for determining fair value has been established that prioritizes inputs to valuation techniques used in fair value calculations. The three levels of inputs are defined as Level 1 (unadjusted quoted prices for identical assets or liabilities in active markets), Level 2 (inputs that are observable in the marketplace other than those inputs classified in Level 1) and Level 3 (inputs that are unobservable in the marketplace). The Company’s financial assets and liabilities measured at fair value on a recurring basis consist of its money market funds, securities available-for-sale, trading securities and foreign currency forward contracts. All other financial instruments are short-term in nature and the carrying amount is reported on the Consolidated Statements of Financial Condition at approximate fair value. Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers Receivables from broker-dealers, clearing organizations and customers include amounts receivable for securities not delivered by the Company to the purchaser by the settlement date (‘‘securities failed-to-deliver’’) and cash deposits held at clearing organizations and clearing brokers to facilitate the settlement and clearance of matched principal transactions. Payables to broker-dealers, clearing organizations and customers include amounts payable for securities not received by the Company from a seller by the settlement date (‘‘securities failed-to-receive’’). Securities failed-to-deliver and securities failed-to-receive for transactions executed between and among institutional investor and broker-dealer clients on a matched principal basis where the Company’s U.S. broker-dealer subsidiary serves as a counterparty to both the buyer and the seller are recorded on a settlement date basis. The Company presents its securities failed-to-deliver and securities failed-to-receive balances on a net-by-counterparty basis within receivables from and payables to broker-dealers, clearing organizations and customers. The difference between the Company’s trade-date receivables and payables for unsettled matched principal transactions reflects commissions earned and is recorded within accounts receivable, net on a trade-date basis. Allowance for Credit Losses All accounts receivable have contractual maturities of less than one year and are derived from trading-related fees and commissions and revenues from products and services. The Company continually monitors collections and payments from its customers and maintains an allowance for doubtful accounts. The allowance for credit losses is based on an estimate of the amount of potential credit losses in existing accounts receivable, as determined from a review of aging schedules, past due balances, historical collection experience and other specific collection issues that have been identified. Account balances are grouped for evaluation based on various risk characteristics, including billing type, legal entity, and geographic region. Additions to the allowance for credit losses are charged to bad debt expense, which is included in general and administrative expense in the Company’s Consolidated Statements of Operations. Balances that are determined to be uncollectable are written off against the allowance for credit losses. The allowance for credit losses was $0.2 million, $0.1 million and $0.1 million as of December 31, 2020, 2019 and 2018, respectively. The provision for bad debts was $0.5 million, $0.3 million and $0.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. Write-offs and other charges against the allowance for credit losses were $0.1 million, $0.1 million and $0.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. Depreciation and Amortization Fixed assets are carried at cost less accumulated depreciation. The Company uses the straight-line method of depreciation over three to seven years. The Company amortizes leasehold improvements on a straight-line basis over the lesser of the life of the improvement or the remaining term of the lease. Software Development Costs The Company capitalizes certain costs associated with the development of internal use software, including among other items, employee compensation and related benefits and third-party consulting costs at the point at which the conceptual formulation, design and testing of possible software project alternatives have been completed. Once the product is ready for its intended use, such costs are amortized on a straight-line basis over three years. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Cloud Computing Costs The Company capitalizes certain costs associated with cloud computing arrangements, including, among other items, employee compensation and related benefits and third-party consulting costs that are part of the application development stage. These costs are setup as a prepaid asset on the balance sheet and are amortized over the period of the hosting service contract. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Foreign Currency Translation and Forward Contracts Assets and liabilities denominated in foreign currencies are translated using exchange rates at the end of the period; revenues and expenses are translated at average monthly rates. Gains and losses on foreign currency translation are a component of accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Transaction gains and losses are recorded in other, net in the Consolidated Statements of Operations. The Company enters into foreign currency forward contracts to hedge its net investment in its U.K. subsidiaries. Gains and losses on these transactions are included in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Revenue Recognition The Company’s classification of revenues in the Consolidated Statements of Operations represents revenues from contracts with customers disaggregated by type of revenue. The Company has four revenue streams as described below. Commission Revenue. The Company charges its broker-dealer clients variable transaction fees for trades executed on its platform and, under certain plans, distribution fees or monthly minimum fees to use the platform for a particular product area. Variable transaction fees are recognized on a trade date basis and generally calculated as a percentage of the notional dollar volume of bonds traded on the platforms and vary based on the type, size, yield and maturity of the bond traded and individual client incentives. Bonds that are more actively traded or that have shorter maturities generally generate lower commissions, while bonds that are less actively traded or that have longer maturities generally command higher commissions. Under the Company’s disclosed trading transaction fee plans, variable transaction fees, distribution fees and unused monthly fee commitments are invoiced and recorded on a monthly basis. For Open Trading trades that the Company executes between and among institutional investor and broker-dealer clients on a matched principal basis by serving as counterparty to both the buyer and the seller, the Company earns its commission through the difference in price between the two trades. The commission is collected upon settlement of the trade, which typically occurs within one to two trading days after the trade date. For U.S. Treasury matched principal trades, commissions are invoiced and recorded on a monthly basis. The following table presents commission revenue by fee type: Year Ended December 31, 2020 2019 2018 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 343,427 $ 266,916 $ 228,004 Open Trading - matched principal trading 170,537 98,080 65,932 U.S. Treasuries - matched principal trading 12,372 2,184 — Total variable transaction fees 526,337 367,180 293,936 Distribution fees and unused minimum fees 108,108 96,676 96,898 Total commissions $ 634,445 $ 463,856 $ 390,834 Information services – Information services includes data licensed to the Company’s broker-dealer clients, institutional investor clients and data-only subscribers; professional and consulting services; technology software licenses; and maintenance and support services. The nature and timing of each performance obligation may vary as these contracts are either subscription-based services transferred over time, and may be net of volume-based discounts, or one-time services that are transferred at a point in time. Revenues for services transferred over time are recognized ratably over the contract period as the Company’s performance obligation is met whereas revenues for services transferred at a point in time are recognized in the period the services are provided. Customers are generally billed monthly, quarterly, or annually; revenues billed in advance are deferred and recognized ratably over the contract period. The following table presents information services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 32,425 $ 29,619 $ 27,475 Services transferred at a point in time 1,916 1,111 752 Total information services revenues $ 34,341 $ 30,730 $ 28,227 Post-trade services – Post-trade services revenue is generated from regulatory transaction reporting, trade publication and trade matching services. Customers are generally billed monthly in arrears and revenue is recognized in the period transactions are processed. Revenues billed in advance are deferred and recognized ratably over the contract period. The Company also generates one-time implementation fees for onboarding clients which are invoiced and recognized in the period the implementation is completed. The following table presents post-trade services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 19,158 $ 15,669 $ 15,013 Services transferred at a point in time 302 94 333 Total post-trade services revenues $ 19,460 $ 15,763 $ 15,346 Other revenues – Other revenues primarily includes revenue from telecommunications line charges to broker-dealer clients. Contract liabilities consist of deferred revenues that the Company records when cash payments are received or due in advance of services to be performed. The revenue recognized from contract liabilities and the remaining balance is shown below: December 31, 2019 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation December 31, 2020 (In thousands) Information services $ 2,138 $ 9,593 $ (8,528 ) $ — $ 3,203 Post-trade services 1,361 15,496 (15,862 ) 50 1,045 Total deferred revenue $ 3,499 $ 25,089 $ (24,390 ) $ 50 $ 4,248 The majority of the Company’s contracts are short-term in nature with durations of less than one-year. For contracts with original durations extending beyond one year, the aggregate amount of the transaction price allocated to remaining performance obligations was $21.1 million as of December 31, 2020. The Company expects to recognize revenue associated with the remaining performance obligations over the next 33 months. Stock-Based Compensation The Company measures and recognizes compensation expense for all share-based payment awards based on their estimated fair values measured as of the grant date. These costs are recognized as an expense in the Consolidated Statements of Operations over the requisite service period, which is typically the vesting period, with an offsetting increase to additional paid-in capital. Forfeitures are recognized as they occur. Income Taxes Income taxes are accounted for using the asset and liability method. Deferred income taxes reflect the net tax effects of temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when such differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is recognized against deferred tax assets if it is more likely than not that such assets will not be realized in future years. The Company recognizes interest and penalties related to unrecognized tax benefits in the provision for income taxes in the Consolidated Statements of Operations. All tax effects related to share-based payments are recorded in the provision for income taxes in the periods during which the awards are exercised or vest. Business Combinations, Goodwill and Intangible Assets Business combinations are accounted for under the purchase method of accounting. The total cost of an acquisition is allocated to the underlying net assets based on their respective estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Determining the fair value of certain assets acquired and liabilities assumed is judgmental in nature and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth rates, customer attrition rates and asset lives. The Company operates as a single reporting unit. Following an acquisition, goodwill no longer retains its identification with a particular acquisition, but instead becomes identifiable with the entire reporting unit. As a result, all of the fair value of the Company is available to support the value of goodwill. An impairment review of goodwill is performed on an annual basis, at year-end, or more frequently if circumstances change. Intangible assets with definite lives, including purchased technologies, customer relationships and other intangible assets, are amortized over their estimated useful lives which range from one to 15 years using either a straight-line or accelerated amortization method based on the pattern of economic benefit the Company expects to realize from such assets. Intangible assets are assessed for impairment when events or circumstances indicate the existence of a possible impairment. Earnings Per Share Basic earnings per share is computed by dividing the net income attributable to common stock by the weighted-average number of shares of common stock outstanding during the period. For purposes of computing diluted earnings per share, the weighted-average shares outstanding of common stock reflects the dilutive effect that could occur if convertible securities or other contracts to issue common stock were converted into or exercised for common stock. Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2020
Brokers And Dealers [Abstract]
Regulatory Capital Requirements	3. Regulatory Capital Requirements Certain U.S. subsidiaries of the Company are registered as a broker-dealer or swap execution facility and therefore are subject to the applicable rules and regulations of the Securities and Exchange Commission (“SEC”) and the Commodity Futures Trading Commission. These rules contain minimum net capital requirements, as defined in the applicable regulations, and also may require a significant part of the registrants’ assets be kept in relatively liquid form. Certain of the Company’s foreign subsidiaries are regulated by the Financial Conduct Authority in the U.K. or other foreign regulators and must maintain financial resources, as defined in the applicable regulations, in excess of the applicable financial resources requirement. As of December 31, 2020, each of the Company’s subsidiaries that are subject to these regulations had net capital or financial resources in excess of their minimum requirements. As of December 31, 2020, the Company’s subsidiaries maintained aggregate net capital and financial resources that were $435.4 million in excess of the required levels of $21.6 million. In August 2020, one of the Company’s U.S. broker-dealer subsidiaries converted to a self-clearing model for the U.S. bond trades to which it is a counterparty via its Open Trading functionality. Previously, these bond transactions were settled through a third-party clearing broker. As a result of this conversion, the broker-dealer subsidiary is required to segregate funds in a special reserve bank account for the benefit of customers pursuant to Rule 15c3-3 of the Securities Exchange Act of 1934. As of December 31, 2020, the broker-dealer subsidiary had a balance of $50.1 million in its special reserve bank account. Each of the Company’s U.S. and foreign regulated subsidiaries are subject to local regulations which generally prohibit repayment of borrowings from the Company or affiliates, paying cash dividends, making loans to the Company or affiliates or otherwise entering into transactions that result in a significant reduction in regulatory net capital or financial resources without prior notification to or approval from such regulated entity’s principal regulator.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2: Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2020 Money market funds $ 20,856 $ — $ — $ 20,856 Trading securities Corporate debt — 19,222 — 19,222 Mutual funds held in rabbi trust — 8,889 — 8,889 Foreign currency forward position — (805 ) — (805 ) Total $ 20,856 $ 27,306 $ — $ 48,162 As of December 31, 2019 Money market funds $ 99,755 $ — $ — $ 99,755 Securities available-for-sale Corporate debt — 137,835 — 137,835 Trading securities Corporate debt — 31,120 — 31,120 U.S. Treasuries — 55,305 — 55,305 Mutual funds held in rabbi trust — 6,217 — 6,217 Foreign currency forward position — (2,772 ) — (2,772 ) Total $ 99,755 $ 227,705 $ — $ 327,460 Securities classified within Level 2 were valued using a market approach utilizing prices and other relevant information generated by market transactions involving comparable assets. The foreign currency forward contracts are classified within Level 2 as the valuation inputs are based on quoted market prices. The mutual funds held in a rabbi trust represent investments associated with the Company’s deferred cash incentive plan. There were no financial assets classified within Level 3 during the years ended December 31, 2020 and 2019. The table below presents the carrying value, fair value and fair value hierarchy category of the Company’s financial assets and liabilities that are not measured at fair value on the Consolidated Statement of Financial Condition. The carrying values of the Company’s financial assets and liabilities not measured at fair value categorized in the fair value hierarchy as Level 1 and Level 2 approximate fair value due to the short-term nature of the underlying assets and liabilities. Carrying Value Fair Value Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2020 Financial assets not measured at fair value: Cash and cash equivalents $ 460,858 $ 460,858 $ 460,858 $ — $ — $ 460,858 Cash segregated under federal regulations 50,059 50,059 50,059 — — 50,059 Accounts receivable, net of allowance 79,577 79,577 — 79,577 — 79,577 Receivables from broker-dealers, clearing organizations and customers 279,915 279,915 97,043 182,872 — 279,915 Total $ 870,409 $ 870,409 $ 607,960 $ 262,449 $ — $ 870,409 Financial liabilities not measured at fair value: Payables to broker-dealers, clearing organizations and customers $ 133,326 $ 133,326 $ — $ 133,326 $ — $ 133,326 As of December 31, 2019 Financial assets not measured at fair value: Cash and cash equivalents $ 270,124 $ 270,124 $ 270,124 $ — $ — $ 270,124 Accounts receivable, net of allowance 62,017 62,017 — 62,017 — 62,017 Total $ 332,141 $ 332,141 $ 270,124 $ 62,017 $ — $ 332,141 The Company enters into foreign currency forward contracts to hedge the net investment in the Company’s U.K. subsidiaries. The Company designates each foreign currency forward contract as a hedge and assesses the risk management objective and strategy, including identification of the hedging instrument, the hedged item and the risk exposure and how effectiveness is to be assessed prospectively and retrospectively. These hedges are for a one-month As of December 31, 2020 2019 (In thousands) Notional value $ 157,057 $ 155,885 Fair value of notional 157,862 158,657 Fair value of the (liability) $ (805 ) $ (2,772 ) The following is a summary of the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value (In thousands) As of December 31, 2020 Trading securities Corporate debt $ 19,081 $ 141 $ — $ 19,222 Mutual funds held in rabbi trust 7,680 1,209 — 8,889 Total investments $ 26,761 $ 1,350 $ — $ 28,111 As of December 31, 2019 Securities available-for-sale Corporate debt $ 137,119 $ 721 $ (5 ) $ 137,835 Trading securities Corporate debt 31,120 14 (14 ) 31,120 U.S. Treasuries 54,738 567 — 55,305 Mutual funds held in rabbi trust 5,173 1,044 — 6,217 Total trading securities 91,031 1,625 (14 ) 92,642 Total investments $ 228,150 $ 2,346 $ (19 ) $ 230,477 The following table summarizes the fair value of the investments based upon the contractual maturities: As of December 31, 2020 2019 (In thousands) Less than one year $ 18,290 $ 120,850 Due in 1 - 5 years 9,821 109,627 Total $ 28,111 $ 230,477 Proceeds from the sales and maturities of investments during the years ended December 31, 2020, 2019 and 2018 were $261.6 million, $262.1 million and $409.3 million, respectively. Net unrealized losses and gains on trading securities were $0.4 million and $0.8 million for the year ended December 31, 2020 and 2019 and were immaterial for the years ended December 31, 2018. Net realized gains were $1.7 million for the year ended December 31, 2020, and were immaterial for the years ended December 31, 2019 and 2018. The following table provides fair values and unrealized losses on corporate debt investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2020 and 2019 respectively: Less than Twelve Months Twelve Months or More Total Fair value Gross unrealized losses Fair value Gross unrealized losses Fair value Gross unrealized losses (In thousands) As of December 31, 2020 Corporate debt $ 1,369 $ — $ — $ — $ — $ — As of December 31, 2019 Corporate debt $ 27,999 $ (18 ) $ 4,406 $ (1 ) $ 32,405 $ (19 )

Receivables from and Payables t

Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers	12 Months Ended
	Dec. 31, 2020
Due To And From Broker Dealers And Clearing Organizations [Abstract]
Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers	5. Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers As of December 31, 2020, receivables from and payables to broker-dealers, clearing organizations and customers consisted of the following: December 31, 2020 Receivables from broker-dealers, clearing organizations and customers: (In thousands) Securities failed-to-deliver - broker-dealers $ 93,294 Securities failed-to-deliver - customers 87,685 Deposits with clearing organizations and broker-dealers 97,043 Other 1,893 Total $ 279,915 Payables to broker-dealers, clearing organizations and customers: Securities failed-to-receive - broker-dealers 70,917 Securities failed-to-receive - customers 60,784 Other 1,625 Total $ 133,326

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Acquisitions	6. Acquisitions On November 1, 2019, the Company and one of its subsidiaries completed their acquisition of all of the outstanding equity interests of LiquidityEdge LLC (“LiquidityEdge” and such acquisition the “LiquidityEdge Acquisition”) pursuant to the terms and conditions of a Unit Purchase Agreement entered into among the Company, LiquidityEdge, the holders of all the outstanding equity interests in LiquidityEdge and certain other persons named therein on August 12, 2019 (as amended, the “Agreement”). The aggregate consideration for the LiquidityEdge Acquisition was $153.2 million, comprised of approximately $104.4 million in cash and 146,450 shares of common stock of the Company (valued at approximately $48.8 million as of the closing date of the LiquidityEdge Acquisition, as described below). A portion of the stock consideration, amounting to 43,937 shares of common stock, was placed in escrow for up to 18 months to secure the sellers’ indemnification obligations under the Agreement. In addition, under the Agreement, the sellers were prohibited from transferring any of the Company common stock received in the LiquidityEdge Acquisition for a period of six months following the November 1, 2019 closing date. The value ascribed to the shares by the Company was discounted from the market value on the date of closing to reflect the non-marketability of such shares during the restriction period. LiquidityEdge is a limited liability company organized in the state of Delaware and is a broker-dealer registered with the SEC and the Financial Industry Regulatory Authority. LiquidityEdge offers an electronic trading platform for U.S. Treasuries. The Company has completed an allocation of the purchase price to the fair value of assets acquired and liabilities assumed at the date of acquisition. The Company utilized an independent third-party to determine the fair value of the acquired intangible assets. The purchase price allocation is as follows (in thousands): Purchase price $ 153,210 Less: acquired cash (2,935 ) Purchase price, net of acquired cash 150,275 Accounts receivable (1,811 ) Intangible assets (58,780 ) Prepaid expenses and other assets (4,168 ) Accounts payable, accrued expenses and other liabilities 2,165 Goodwill $ 87,681 The acquired intangible assets and useful lives are as follows ($ in thousands): Costs Useful Lives Customer relationships $ 58,690 15 years Tradename - finite life 90 1 year Total $ 58,780 On November 30, 2020 the Company acquired Regulatory Services GmbH, the pan-European regulatory reporting business of Deutsche Börse Group. The purchase price consists of In September 2020, the Company entered into an agreement to acquire MuniBrokers LLC, a central electronic venue serving municipal bond inter-dealer brokers and dealers. The acquisition is expected to close in the first half of 2021, subject to the satisfaction of customary closing conditions.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	7 . Goodwill and Intangible Assets Goodwill and intangible assets with indefinite lives was $147.4 and $146.9 million as of December 31, 2020 and December 31, 2019. Intangible assets that are subject to amortization, including the related accumulated amortization, are comprised of the following: December 31, 2020 December 31, 2019 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Technology $ 5,770 $ (5,770 ) $ — $ 5,770 $ (5,770 ) $ — Customer relationships 102,696 (7,369 ) 95,327 64,332 (3,451 ) 60,881 Non-competition agreements 380 (380 ) — 380 (380 ) — Tradenames and patents 400 (373 ) 27 490 (385 ) 105 Total $ 109,246 $ (13,892 ) $ 95,354 $ 70,972 $ (9,986 ) $ 60,986 Amortization expense associated with identifiable intangible assets was $3.9 million, $0.8 million and $0.4 million for the years ended December 31, 2020, 2019 and 2018, respectively. Annual estimated total amortization expense is $5.7 million, $6.9 million, $7.9 million, $6.7 million and $5.7 million for 2021 through 2025.

Capitalized Software, Furniture

Capitalized Software, Furniture, Equipment and Leasehold Improvements	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Capitalized Software, Furniture, Equipment and Leasehold Improvements	8. Capitalized Software, Furniture, Equipment and Leasehold Improvements Capitalized software development costs, furniture, equipment and leasehold improvements, net of accumulated depreciation and amortization, are comprised of the following: As of December 31, 2020 2019 (In thousands) Software development costs $ 151,139 $ 119,911 Computer hardware and related software 52,696 48,379 Office hardware 8,782 5,725 Furniture and fixtures 7,078 5,000 Leasehold improvements 29,064 27,966 248,759 206,981 Accumulated depreciation and amortization (163,555 ) (135,186 ) Total $ 85,204 $ 71,795 During the years ended December 31, 2020 and 2019, software development costs totaling $30.6 million and $22.4 million, respectively, were capitalized. Non-capitalized software costs and routine maintenance costs are expensed as incurred and are included in employee compensation and benefits and professional and consulting fees in the Consolidated Statements of Operations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The provision for income taxes consists of the following: Year Ended December 31, 2020 2019 2018 (In thousands) Current: Federal $ 30,215 $ 28,928 $ 31,617 State and local 19,130 7,686 5,928 Foreign 15,538 13,234 8,862 Total current provision 64,883 49,848 46,407 Deferred: Federal 7,474 2,579 (1,416 ) State and local 1,439 403 (272 ) Foreign 1,186 (308 ) 515 Total deferred provision 10,099 2,674 (1,173 ) Provision for income taxes $ 74,982 $ 52,522 $ 45,234 Pre-tax income from U.S. operations was $288.3 million, $190.4 million and $168.5 million for the years ended December 31, 2020, 2019 and 2018, respectively. Pre-tax income from foreign operations was $86.1 million, $67.0 million and $49.6 million for the years ended December 31, 2020, 2019 and 2018, respectively. The difference between the Company’s reported provision for income taxes and the U.S. federal statutory rate of 21% is as follows: Year Ended December 31, 2020 2019 2018 U.S. federal tax at statutory rate 21.0 % 21.0 % 21.0 % State and local taxes - net of federal benefit 4.4 2.5 2.0 Credits and deductions related to research activities (0.3 ) (0.3 ) (0.3 ) Foreign rate differential benefit (0.4 ) (0.5 ) (0.5 ) Excess tax benefit from stock-based compensation (5.4 ) (3.5 ) (2.1 ) Other, net 0.7 1.2 0.6 Provision for income taxes 20.0 % 20.4 % 20.7 % The following is a summary of the Company’s net deferred tax assets: As of December 31, 2020 2019 (In thousands) Deferred tax assets: Stock compensation expense $ 3,682 $ 4,926 Operating lease liabilities 19,339 20,227 Other 1,968 892 Total deferred tax assets 24,989 26,045 Valuation allowance — — Net deferred tax assets 24,989 26,045 Deferred tax liabilities: Depreciation and amortization (9,729 ) (4,085 ) Capitalized software development costs (7,828 ) (5,306 ) Goodwill and intangible assets (2,852 ) (1,120 ) Operating lease right-of-use assets (15,600 ) (16,515 ) Deferred tax (liability) asset, net $ (11,020 ) $ (981 ) The Company or one of its subsidiaries files U.S. federal, state and foreign income tax returns. The Company is currently under a New York State income tax examination for tax years 2010 through 2017 and a New York City income tax examination for the tax years 2016 through 2018. At this time, the Company cannot estimate when the examinations will conclude or the impact such examinations will have on the Company’s Consolidated Financial Statements, if any. Generally, other than New York City and State, the Company is no longer subject to tax examinations by tax authorities for years prior to 2017. A reconciliation of the unrecognized tax benefits is as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Balance at beginning of year $ 6,831 $ 4,718 $ 2,650 Additions attributable to state and local tax apportionment 9,486 2,113 2,068 Balance at end of year $ 16,317 $ 6,831 $ 4,718 As of December 31, 2020, the Company recorded $16.3 million of unrecognized tax benefits which, if recognized, would affect the Company’s effective tax rate. Due to the uncertainty related to the timing and potential outcome of audits, the Company cannot reasonably estimate the amount of the unrecognized tax benefit that could be adjusted in the next 12 months. During the years ended December 31, 2020, 2019 and 2018, the Company recognized $3.7 million, $0.6 million and $0.4 million, respectively, in penalties and interest. The Company had $4.9 million and $1.2 million accrued for the payment of interest and penalties at December 31, 2020 and 2019, respectively.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity Common Stock As of December 31, 2020 and 2019, the Company had 110,000,000 authorized shares of voting common stock and 10,000,000 authorized shares of non-voting common stock. Voting common stock entitles the holder to one vote per share of common stock held. The following is a summary of the change in the Company’s outstanding shares of voting common stock: Year Ended December 31, 2020 2019 2018 (In thousands) Outstanding shares of voting common stock at the beginning of year 37,936 37,640 37,621 Exercise of stock options 177 147 121 Issuance of restricted stock, net of cancellations 56 161 67 Shares withheld for withholding tax payments (125 ) (98 ) (45 ) Treasury shares used for acquisition — 146 — Repurchases (39 ) (60 ) (124 ) Outstanding shares of voting common stock at the end of year 38,005 37,936 37,640 In September 2017, the Board of Directors authorized a fifteen-month two-year Dividends During 2020, 2019 and 2018, the Company paid quarterly cash dividends of $0.60 per share, $0.51 per share and $0.42 per share, respectively. Any future declaration and payment of dividends will be at the sole discretion of the Company’s Board of Directors. The Board of Directors may take into account such matters as general business conditions, the Company’s financial results, capital requirements, contractual obligations, legal, and regulatory restrictions on the payment of dividends to the Company’s stockholders or by the Company’s subsidiaries to their respective parent entities, and any such other factors as the Board of Directors may deem relevant.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Plans	11. Stock-Based Compensation Plans The Company maintains stock incentive plans which provide for the grant of stock options, stock appreciation rights, restricted stock, restricted stock units, performance shares, performance units, or other stock-based awards as incentives and rewards to encourage employees, consultants and non-employee directors to participate in the long-term success of the Company. As of December 31, 2020, there were 2,531,199 shares available for grant under the stock incentive plans. Total stock-based compensation expense was as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Employees: Restricted stock and performance shares $ 21,310 $ 20,182 $ 12,559 Stock options 3,100 4,032 2,193 24,410 24,214 14,752 Non-employee directors: Restricted stock 1,203 1,080 1,098 Total stock-based compensation $ 25,613 $ 25,294 $ 15,850 The Company records stock-based compensation expense for employees in employee compensation and benefits and for non-employee directors in general and administrative expenses in the Consolidated Statements of Operations. Stock Options The exercise price of each option granted is equal to the market price of the Company’s common stock on the date of grant. Generally, option grants have provided for vesting over a three or five-year The weighted-average fair value for options granted during 2020, 2019 and 2018 was $91.43, $58.37 and $56.11, respectively. The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted, excluding the two awards discussed below: Year Ended December 31, 2020 2019 2018 Expected life (years) 5.0 5.0 5.0 Risk-free interest rate 1.6 % 2.6 % 2.2 % Expected volatility 26.8 % 25.9 % 26.9 % Expected dividend yield 0.6 % 0.8 % 0.8 % In addition to the option grants above, 76,868 stock options were granted to the Company’s President and Chief Operating Officer in January 2019 with an aggregate grant date fair value of $2.9 million as determined by an independent third party using a Monte Carlo simulation model. The exercise price is $272.88 for 35,679 of the stock options and $294.71 for the remaining 41,189 stock options, which is equal to 125% and 135%, respectively, of the fair market value of the Company’s common stock on the grant date. Subject to the grantee’s continued service with the Company, the options will vest and become exercisable on January 22, 2024. The options expire on July 22, 2024. Key assumptions used for the Monte Carlo model included a risk-free interest rate of 2.6%, volatility of 25.8% and a dividend yield of 0.8%. In November 2018, 148,524 stock options were granted to the Company’s Chief Executive Officer with a grant date fair value of $5.5 million as determined by an independent third party using a Monte Carlo simulation model. The exercise price is $257.78 for 69,113 of the stock options and $278.40 for the remaining 79,411 stock options, which is equal to 125% and 135%, respectively, of the fair market value of the Company’s stock on the grant date. Subject to the grantee’s continued service with the Company, the options will vest and become exercisable on November 8, 2023. The options expire on May 8, 2024. Key assumptions used for the Monte Carlo model included a risk-free interest rate of 3.1%, volatility of 25.9% and a dividend yield of 0.8%. The following table reports stock option activity during the three years ended December 31, 2020 and the intrinsic value as of December 31, 2020: Number of Shares Weighted-Average Exercise Price ($) Remaining Contractual Term Intrinsic Value ($) (In thousands) Outstanding at December 31, 2017 529,611 67.60 Granted 168,217 261.19 Canceled (1,676 ) 142.69 Exercised (120,588 ) 24.66 Outstanding at December 31, 2018 575,564 132.93 Granted 82,474 279.57 Canceled (548 ) 198.67 Exercised (106,899 ) 28.24 Outstanding at December 31, 2019 550,591 175.16 Granted 13,900 368.10 Canceled (218 ) 307.52 Exercised (176,901 ) 84.07 76,709 Outstanding at December 31, 2020 387,372 223.60 2.8 134,401 Exercisable at December 31, 2020 99,415 137.78 1.7 43,025 The intrinsic value is the amount by which the closing price of the Company’s common stock on December 31, 2020 of $570.56 or the price on the day of exercise exceeds the exercise price of the stock options multiplied by the number of shares. As of December 31, 2020, there was $5.9 million of total unrecognized compensation cost related to non-vested stock options. That cost is expected to be recognized over a weighted-average period of 2.4 years. Restricted Stock and Performance Shares Restricted stock generally vests over a three or five-year Prior to 2020, performance shares were generally granted with a performance period of one year, whereby each performance share award was earned or forfeited based on the level of achievement by the Company of pre-tax operating income, as defined in the year following the grant. The pay-out ranged from zero to 150% of the performance share award. For each performance share earned, a participant was awarded an equal number of shares of restricted stock. Subject to the grantee’s continued service, any restricted stock awarded to a participant vested in two equal installments on each of the second and third anniversaries of the date of grant of the applicable performance share award. Compensation expense for one-year performance shares was measured at the grant date and recognized on a graded basis over the vesting period. The following table reports performance share activity for the one-year performance awards for the two years ended December 31, 2019: Performance year: 2019 2018 Target share pay-out 16,716 10,479 Actual share pay-out (paid in following year) 19,401 10,479 Weighted average fair value per share on grant date $ 223.81 $ 202.04 Beginning in 2020, performance shares were granted with a three-year In addition to the grants above, 18,914 performance shares were granted to the Company’s President and Chief Operating Officer in January 2019 with an aggregate fair value of $2.9 million as determined by an independent third party using a Monte Carlo simulation model. The performance share award provides that the number of shares earned will be based on the Company’s achievement of certain share price levels during the five-year In November 2018, 37,742 performance shares were granted to the Company’s Chief Executive Officer with a grant date fair value of $5.5 million as determined by an independent third party using a Monte Carlo simulation model. The performance share award provides that the number of shares earned will be based on the Company’s achievement of certain share price levels during the five-year The following table reports restricted stock and performance share activity during the three years ended December 31, 2020: Number of Restricted Shares Weighted-Average Grant Date Fair Value Outstanding at December 31, 2017 319,599 $ 88.77 Granted 59,179 Performance share pay-out 8,094 Canceled (4,046 ) Vested (110,956 ) Outstanding at December 31, 2018 271,870 $ 112.47 Granted 118,632 Performance share pay-out 87,163 Canceled (2,321 ) Vested (129,312 ) Outstanding at December 31, 2019 346,032 $ 154.27 Granted 38,907 Performance share pay-out 19,401 Canceled (3,480 ) Vested (170,213 ) Outstanding at December 31, 2020 230,647 $ 224.63 As of December 31, 2020, there was $27.0 million of total unrecognized compensation expense related to non-vested restricted stock and performance shares. That cost is expected to be recognized over a weighted-average period of 1.5 years. Employee Stock Purchase Plan The Company offers a non-qualified employee stock purchase plan for non-executive employees. Under the plan, participants are granted the right to purchase shares of common stock based on the fair market value on the last day of the six-month offering period. On the purchase date, the Company grants to the participants a number of shares of common stock equal to 20% of the aggregate shares purchased by the participant. These matching shares vest over a one-year

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	12. Earnings Per Share The following table sets forth basic and diluted weighted average shares outstanding used to compute earnings per share: Year Ended December 31, 2020 2019 2018 (In thousands, except per share amounts) Basic weighted average shares outstanding 37,359 37,083 36,958 Dilutive effect of stock options and restricted stock 785 873 897 Diluted weighted average shares outstanding 38,144 37,956 37,855 Basic earnings per share $ 8.01 $ 5.53 $ 4.68 Diluted earnings per share $ 7.85 $ 5.40 $ 4.57 Stock options and restricted stock totaling 21,127 shares, 146,822 shares and 83,718 shares for the years ended December 31, 2020, 2019 and 2018, respectively, were excluded from the computation of diluted earnings per share because their effect would have been antidilutive. The computation of diluted shares can vary among periods due, in part, to the change in the average price of the Company’s common stock.

Credit Agreement

Credit Agreement	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Credit Agreement	13. Credit Agreements Revolving Credit Agreement In October 2015, the Company entered into a two-year November 2020 one-year In November 2020, the Company entered into a credit agreement (the “Credit Agreement”) with a syndicate of lenders and JPMorgan Chase Bank, N.A., as administrative agent, that provides aggregate commitments totaling $500 million, consisting of a revolving credit facility and a $5 million letter of credit sub-limit for standby letters of credit. The Credit Agreement replaced the Prior Credit Agreement and will mature on November 12, 2021, with the Company’s option to request up to two additional 364-day extensions at the discretion of each lender and subject to customary conditions. Subject to satisfaction of certain specified conditions, the Company is permitted to upsize the Credit Agreement by up to $250 million in total. Borrowings under the Credit Agreement will bear interest at a rate per annum equal to the base rate or adjusted LIBOR plus an applicable margin that varies with the Company’s consolidated total leverage ratio. The Credit Agreement requires that the Company satisfy certain covenants, which include leverage ratios and minimum earnings before interest, tax, and depreciation and amortization (“EBITDA”) requirements. The Company was in compliance with all applicable covenants at December 31, 2020. The Company incurred an aggregate of $0.8 million of interest expense on borrowings under the Credit Agreement and the Prior Credit Agreement for the year ended December 31, 2020. Collateralized Agreement In connection with its self-clearing operations, one of the Company’s broker-dealer subsidiaries entered into an agreement (the “Collateralized Agreement”) with its settlement bank to provide loans to the subsidiary in amounts up to an aggregate of $200.0 million on an uncommitted basis. Borrowings under the Collateralized Agreement are collateralized by securities pledged by the Company’s broker-dealer subsidiary to the settlement bank, subject to applicable haircuts and concentration limits. Borrowings under the Collateralized Agreement will bear interest at a rate per annum equal to the Federal Funds Rate plus 1.00%. The Company incurred $0.1 million of interest expense on borrowings under the Collateralized Agreement during the year ended December 31, 2020. As of December 31, 2020, the Company had no borrowings outstanding and $200.0 million in available borrowing capacity under the Collateralized Agreement.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	14. Leases The Company has operating leases for corporate offices with initial lease terms ranging from one-year The following table presents the components of occupancy expense for the years ended December 31, 2020 and 2019: Lease cost: Classification 2020 2019 (In thousands) Operating lease cost Occupancy $ 13,455 $ 10,875 Operating lease cost for subleased/assigned properties Other, net 2,404 2,422 Variable lease costs Occupancy 26 169 Sublease income for subleased/assigned properties Other, net (2,420 ) (2,422 ) Net lease cost $ 13,465 $ 11,044 The Company determines whether an arrangement is, or includes, a lease at contract inception. Operating lease right-of-use assets and liabilities are recognized at commencement date and are initially measured based on the present value of lease payments over the defined lease term. As the Company’s leases do not provide an implicit rate, the Company used its incremental borrowing rate based on the information available at the adoption date in determining the present value of lease payments. The weighted average remaining lease term and weighted average discount rate are as follows: As of December 31, Lease Term and Discount Rate 2020 2019 Weighted average remaining lease term (in years) 12.3 13.3 Weighted average discount rate 5.9 % 5.9 % The following table presents the maturity of lease liabilities as of December 31, 2020: (In thousands) 2021 $ 12,131 2022 10,516 2023 10,270 2024 10,937 2025 10,937 2026 and thereafter 79,003 Total lease payments 133,794 Less: interest 40,182 Present value of lease liabilities $ 93,612 The Company has entered into agreements to sublease or assign the Company’s lease obligations on two properties to third parties and is contingently liable should the third parties default on future lease obligations through the lease termination dates of February 2022 and May 2022. The aggregate amount of the future lease obligations under these arrangements is $2.1 million as of December 31, 2020.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. Commitments and Contingencies Legal In the normal course of business, the Company and its subsidiaries included in the consolidated financial statements may be involved in various lawsuits, proceedings and regulatory examinations. The Company assesses its liabilities and contingencies in connection with outstanding legal proceedings, if any, utilizing the latest information available. For matters where it is probable that the Company will incur a material loss and the amount can be reasonably estimated, the Company would establish an accrual for the loss. Once established, the accrual would be adjusted to reflect any relevant developments. When a loss contingency is not both probable and estimable, the Company does not establish an accrual. Based on currently available information, the outcome of the Company’s outstanding matters is not expected to have a material adverse impact on the Company’s financial position. It is not presently possible to determine the ultimate exposure to these matters and there is no assurance that the resolution of the outstanding matters will not significantly exceed any reserves accrued by the Company. Other The Company, through certain of its subsidiaries, executes bond transactions between its institutional investor and broker-dealer clients on a matched principal basis by serving as counterparty to both the buyer and the seller in trades. In August 2020, one of the Company’s U.S. broker-dealer subsidiaries converted to a self-clearing model for the settlement of such transactions. The Company’s other U.S. and U.K subsidiaries continue to settle their transactions through third-party clearing brokers. Settlement typically occurs within one to two trading days after the trade date. Cash settlement of the transaction occurs upon receipt or delivery of the underlying instrument that was traded. Under both the self-clearing and the third-party clearing broker models, the Company is exposed to credit risk in the event a counterparty does not fulfill its obligation to complete a transaction or if there is a miscommunication or other error in executing a matched principal transaction. Pursuant to the terms of the securities clearing agreements, each third-party clearing broker has the right to charge the Company for any losses they suffer resulting from a counterparty’s failure on any of the Company’s trades. The Company did not record any liabilities or losses with regard to counterparty failures for the three years ended December 31, 2020. In the normal course of business, the Company enters into contracts that contain a variety of representations, warranties and general indemnifications. The Company’s maximum exposure under these arrangements is unknown, as this would involve future claims that may be made against the Company that have not yet occurred. However, based on experience, the Company expects the risk of loss to be remote.

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment and Geographic Information	16. Segment and Geographic Information The Company operates an electronic multi-party platform for the trading of fixed-income securities and provides related data, analytics, compliance tools and post-trade services. The Company’s operations constitute a single For the years ended December 31, 2020, 2019 and 2018, the U.K. was the only individual foreign country in which the Company had a subsidiary that accounted for 10% or more of the total revenues or total long-lived assets. Revenues and long-lived assets are attributed to geographic area based on the location of the particular subsidiary. Long-lived assets are defined as furniture, equipment, leasehold improvements and capitalized software. Revenues for the three years ended December 31, 2020, 2019 and 2018 and long-lived assets as of December 31, 2020 and 2019 were as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Revenues Americas $ 583,164 $ 427,276 $ 369,324 Europe 89,751 74,511 59,943 Asia 16,210 9,565 6,298 Total $ 689,125 $ 511,352 $ 435,565 As of December 31, 2020 2019 (In thousands) Long-lived assets, as defined Americas $ 68,707 $ 62,376 Europe 16,491 9,410 Asia 6 9 Total $ 85,204 $ 71,795

Retirement and Deferred Compens

Retirement and Deferred Compensation Plans	12 Months Ended
	Dec. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Retirement and Deferred Compensation Plans	17. Retirement and Deferred Compensation Plans The Company, through its U.S. and U.K. subsidiaries, offers its employees the opportunity to invest in defined contribution plans. For the years ended December 31, 2020, 2019 and 2018, the Company contributed $4.0 million, $3.3 million and $2.6 million, respectively, to the plans. The Company offers a non-qualified deferred cash incentive plan to certain officers and other employees. Under the plan, eligible employees may defer up to 100% of their annual cash incentive pay. The Company has elected to fund its deferred compensation obligations through a rabbi trust. The rabbi trust is subject to creditor claims in the event of insolvency but such assets are not available for general corporate purposes. Assets held in the rabbi trust are invested in mutual funds, as selected by the participants, which are designated as trading securities and carried at fair value. As of December 31, 2020 and 2019, the fair value of the mutual fund investments and deferred compensation obligations were $8.9 million and $6.2 million, respectively. Changes in the fair value of securities held in the rabbi trust and offsetting increases or decreases in the deferred compensation obligation are recognized in other, net in the Company’s Consolidated Statements of Operations.

Cash and Cash Equivalents and R

Cash and Cash Equivalents and Restricted Cash	12 Months Ended
	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Cash and Cash Equivalents and Restricted Cash	18. Cash and Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash and cash equivalents together with restricted or segregated cash as reported within the Consolidated Statements of Financial Condition to the sum of the same such amounts shown in the Consolidated Statements of Cash Flows: Statement of Financial Condition Location December 31, 2020 December 31, 2019 (In thousands) Cash and cash equivalents Cash and cash equivalents $ 460,858 $ 270,124 Cash segregated for regulatory purposes Cash segregated under federal regulations 50,059 — Deposits with clearing organizations and broker-dealers Receivables from broker-dealers, clearing organizations and customers 97,043 — Other deposits Prepaid expenses and other assets 90 4,129 Total $ 608,050 $ 274,253

Parent Company Information

Parent Company Information	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Parent Company Information	19. Parent Company Information The following tables present Parent Company–only financial information and should be read in conjunction with the consolidated financial statements of the Company. MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Financial Condition As of December 31, 2020 December 31, 2019 (In thousands) ASSETS Cash and cash equivalents $ 55,747 $ 48,241 Investments, at fair value 4,811 141,318 Accounts receivable 178 63 Receivable from subsidiaries 41,986 5,997 Intangible assets, net of accumulated amortization 27 30 Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization 23,518 25,247 Operating lease right-of-use assets 64,460 68,559 Investments in subsidiaries 853,626 570,145 Prepaid expenses and other assets 4,591 6,978 Income and other tax receivable 9,028 3,219 Total assets $ 1,057,972 $ 869,797 LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities Accrued employee compensation $ 10,241 $ 6,543 Income and other tax liabilities 3,457 — Accounts payable, accrued expenses and other liabilities 9,341 9,254 Operating lease liabilities 79,872 83,909 Total liabilities 102,911 99,706 Stockholders' equity Preferred stock — — Series A Preferred Stock — — Common stock voting 123 122 Common stock non-voting — — Additional paid-in capital 329,742 342,541 Treasury stock (169,523 ) (153,388 ) Retained earnings 799,369 591,086 Accumulated other comprehensive loss (4,650 ) (10,270 ) Total stockholders' equity 955,061 770,091 Total liabilities and stockholders' equity $ 1,057,972 $ 869,797 MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Operations and Comprehensive Income Year Ended December 31, 2020 2019 2018 (In thousands) Dividends from subsidiary $ 30,000 $ 165,000 $ 130,000 Expenses Employee compensation and benefits 19,710 16,100 10,785 Depreciation and amortization 2,068 1,919 1,760 Technology and communications 10 13 43 Professional and consulting fees 7,332 6,523 4,932 Occupancy 162 850 7,381 General and administrative 2,551 2,252 1,513 Total expenses 31,833 27,657 26,414 Operating (loss) income (1,833 ) 137,343 103,586 Other income (expense) Investment income 2,799 5,305 3,835 Interest expense (805 ) — — Other, net (318 ) (1,344 ) (711 ) Total other income 1,676 3,961 3,124 (Loss) income before income taxes and equity in undistributed earnings of subsidiaries (157 ) 141,304 106,710 Provision for income taxes (23,444 ) (9,442 ) (7,350 ) Income before equity in undistributed income of subsidiaries 23,287 150,746 114,060 Equity in undistributed income of subsidiaries 276,090 54,156 58,792 Net income 299,377 204,902 172,852 Other comprehensive income (loss), net 5,620 2,124 (2,168 ) Comprehensive income $ 304,997 $ 207,026 $ 170,684 MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Cash Flows Year Ended December 31, 2020 2019 2018 (In thousands) Cash flows from operating activities Net income $ 299,377 $ 204,902 $ 172,852 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 2,068 1,919 1,760 Amortization of operating lease right-of-use assets 4,117 4,027 — Stock-based compensation expense 10,834 10,547 5,801 Deferred taxes 3,644 1,255 (2,515 ) Equity in undistributed income of subsidiaries (276,090 ) (54,156 ) (58,792 ) Other (671 ) 328 710 Changes in operating assets and liabilities: (Increase) in accounts receivable (115 ) (4 ) (14 ) (Increase) decrease in receivable from subsidiaries (25,049 ) 5,253 15,985 (Increase) decrease in prepaid expenses and other assets (1,085 ) 933 (782 ) (Increase) in mutual funds held in rabbi trust (1,328 ) (1,183 ) (470 ) Increase in accrued employee compensation 3,698 876 567 (Increase) in income and other tax receivable (1,240 ) (3,219 ) — Increase (decrease) in income and other tax liabilities 6,676 (2,612 ) 469 (Decrease) increase in accounts payable, accrued expenses and other liabilities (442 ) (2,039 ) 13,619 (Decrease) increase in operating lease liabilities (4,055 ) 1,191 — Net cash provided by operating activities 20,339 168,018 149,190 Cash flows from investing activities Acquisition of business, net of cash and cash equivalents acquired — (102,320 ) — Available-for-sale investments Proceeds from maturities and sales 170,657 170,936 333,791 Purchases (32,865 ) (160,827 ) (336,533 ) Purchases of furniture, equipment and leasehold improvements (337 ) (1,424 ) (24,786 ) Purchase of intangible asset — (30 ) — Net cash provided by (used in) investing activities 137,455 (93,665 ) (27,528 ) Cash flows from financing activities Cash dividend on common stock (90,566 ) (76,231 ) (62,432 ) Exercise of stock options 4,007 1,207 2,973 Withholding tax payments on restricted stock vesting and stock option exercises (42,418 ) (25,820 ) (8,043 ) Repurchases of common stock (16,135 ) (17,256 ) (25,171 ) Proceeds from short-term borrowings 348,000 — — Repayments of short-term borrowings (348,000 ) — — Net cash (used in) financing activities (145,112 ) (118,100 ) (92,673 ) Effect of exchange rate changes on investments (5,176 ) (3,852 ) 4,129 Cash and cash equivalents including restricted cash Net increase (decrease) for the period 7,506 (47,599 ) 33,118 Beginning of period 48,241 95,840 62,722 End of period $ 55,747 $ 48,241 $ 95,840 Supplemental cash flow information: Cash paid for income taxes $ 32,674 $ 41,025 $ 37,721 Cash paid for interest 805 — — Non-cash investing and financing activity: Exercise of stock options - cashless $ 10,866 $ 1,811 $ — Treasury stock used for acquisition of business — (48,830 ) —

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated. Certain reclassifications have been made to the prior periods’ consolidated financial statements in order to conform to the current period presentation. Such reclassifications are immaterial, individually and in the aggregate, to both current and all previously issued financial statements taken as a whole and have no effect on previously reported net income.
Accounting Pronouncements, Recently Adopted	Accounting Pronouncements, Recently Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2018-15, “Intangibles—Goodwill and Other—Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract” (“ASU 2018-15”). The standard requires the capitalization of implementation costs incurred in a cloud computing arrangement to be aligned with the requirements for capitalizing costs incurred to develop or obtain internal-use software. The Company adopted ASU 2018-15 effective July 1, 2019 on a prospective basis. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In January 2017, the FASB issued ASU 2017-04, “Intangibles-Goodwill and Other” (“ASU 2017-04”). ASU 2017-04 simplifies the testing for goodwill impairment, which eliminates the requirement to determine the fair value of individual assets and liabilities of a reporting unit to measure goodwill impairment. Instead, goodwill impairment testing will be performed by comparing the fair value of the reporting unit with its carrying amount and recognizing impairment by which the carrying amount exceeds the reporting unit’s fair value. The Company adopted ASU 2017-04 effective January 1, 2020 on a prospective basis. Adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In June 2016, the FASB issued ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326) -Measurement of Credit Losses on Financial Instruments”. This ASU amends several aspects of the measurement of credit losses on financial instruments, including replacing the existing incurred credit loss model and other models with the Current Expected Credit Losses model (“CECL”). Under CECL, the allowance for losses for financial assets that are measured at amortized cost reflects management’s estimate of credit losses over the remaining expected life of the financial assets. Expected credit losses for newly recognized financial assets, as well as changes to expected credit losses during the period, would be recognized in earnings. Expected credit losses will be measured based on historical experience, current conditions and forecasts that affect the collectability of the reported amount. The Company adopted this ASU on January 1, 2020 using the modified retrospective method of adoption. Adoption of this ASU did not have a material impact on the Company's Consolidated Financial Statements.
Accounting Pronouncements, Not Yet Adopted	Accounting Pronouncements, Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting”, which is designed to ease the potential burden in accounting for the transition away from LIBOR. The ASU applies to contracts, hedging relationships, and other transactions that reference LIBOR or another reference rate expected to be discontinued and replaced with alternative reference rates as a result of reference rate reform. The ASU provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. The ASU was effective for all entities as of March 12, 2020 and can be adopted from this date through December 31, 2022. The Company does not expect adoption of this ASU to have a material impact on its Consolidated F inancial S tatements.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company defines cash equivalents as short-term interest-bearing investments with maturities at the time of purchase of three months or less.
Investments	Investments The Company determines the appropriate classification of securities at the time of purchase which are recorded in the Consolidated Statements of Financial Condition on the trade date. Securities are classified as available-for-sale or trading. The Company’s available-for-sale investments are comprised of investment-grade corporate debt securities. Available-for-sale investments are carried at fair value with the unrealized gains or losses reported in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Trading investments include investment-grade corporate debt securities and U.S. Treasuries and are carried at fair value, with realized and unrealized gains or losses included in other, net in the Consolidated Statements of Operations. The Company assesses whether an other-than-temporary impairment loss on the available-for-sale investments has occurred due to declines in fair value or other market conditions. The portion of an other-than-temporary impairment related to credit loss is recorded as a charge in the Consolidated Statements of Operations. The remainder is recognized in accumulated other comprehensive loss if the Company does not intend to sell the security and it is more likely than not that the Company will not be required to sell the security prior to recovery. No charges for other-than-temporary losses were recorded during the years ended December 31, 2020, 2019 and 2018.
Fair Value Financial Instruments	Fair Value Financial Instruments Fair value is defined as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” A three-tiered hierarchy for determining fair value has been established that prioritizes inputs to valuation techniques used in fair value calculations. The three levels of inputs are defined as Level 1 (unadjusted quoted prices for identical assets or liabilities in active markets), Level 2 (inputs that are observable in the marketplace other than those inputs classified in Level 1) and Level 3 (inputs that are unobservable in the marketplace). The Company’s financial assets and liabilities measured at fair value on a recurring basis consist of its money market funds, securities available-for-sale, trading securities and foreign currency forward contracts. All other financial instruments are short-term in nature and the carrying amount is reported on the Consolidated Statements of Financial Condition at approximate fair value.
Receivables from and Payables to Broker- dealers, Clearing Organizations and Customers	Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers Receivables from broker-dealers, clearing organizations and customers include amounts receivable for securities not delivered by the Company to the purchaser by the settlement date (‘‘securities failed-to-deliver’’) and cash deposits held at clearing organizations and clearing brokers to facilitate the settlement and clearance of matched principal transactions. Payables to broker-dealers, clearing organizations and customers include amounts payable for securities not received by the Company from a seller by the settlement date (‘‘securities failed-to-receive’’). Securities failed-to-deliver and securities failed-to-receive for transactions executed between and among institutional investor and broker-dealer clients on a matched principal basis where the Company’s U.S. broker-dealer subsidiary serves as a counterparty to both the buyer and the seller are recorded on a settlement date basis. The Company presents its securities failed-to-deliver and securities failed-to-receive balances on a net-by-counterparty basis within receivables from and payables to broker-dealers, clearing organizations and customers. The difference between the Company’s trade-date receivables and payables for unsettled matched principal transactions reflects commissions earned and is recorded within accounts receivable, net on a trade-date basis.
Allowance for Credit Losses	Allowance for Credit Losses All accounts receivable have contractual maturities of less than one year and are derived from trading-related fees and commissions and revenues from products and services. The Company continually monitors collections and payments from its customers and maintains an allowance for doubtful accounts. The allowance for credit losses is based on an estimate of the amount of potential credit losses in existing accounts receivable, as determined from a review of aging schedules, past due balances, historical collection experience and other specific collection issues that have been identified. Account balances are grouped for evaluation based on various risk characteristics, including billing type, legal entity, and geographic region. Additions to the allowance for credit losses are charged to bad debt expense, which is included in general and administrative expense in the Company’s Consolidated Statements of Operations. Balances that are determined to be uncollectable are written off against the allowance for credit losses. The allowance for credit losses was $0.2 million, $0.1 million and $0.1 million as of December 31, 2020, 2019 and 2018, respectively. The provision for bad debts was $0.5 million, $0.3 million and $0.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. Write-offs and other charges against the allowance for credit losses were $0.1 million, $0.1 million and $0.2 million for the years ended December 31, 2020, 2019 and 2018, respectively.
Depreciation and Amortization	Depreciation and Amortization Fixed assets are carried at cost less accumulated depreciation. The Company uses the straight-line method of depreciation over three to seven years. The Company amortizes leasehold improvements on a straight-line basis over the lesser of the life of the improvement or the remaining term of the lease.
Software Development Costs	Software Development Costs The Company capitalizes certain costs associated with the development of internal use software, including among other items, employee compensation and related benefits and third-party consulting costs at the point at which the conceptual formulation, design and testing of possible software project alternatives have been completed. Once the product is ready for its intended use, such costs are amortized on a straight-line basis over three years. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable.
Cloud Computing Costs	Cloud Computing Costs The Company capitalizes certain costs associated with cloud computing arrangements, including, among other items, employee compensation and related benefits and third-party consulting costs that are part of the application development stage. These costs are setup as a prepaid asset on the balance sheet and are amortized over the period of the hosting service contract. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable.
Foreign Currency Translation and Forward Contracts	Foreign Currency Translation and Forward Contracts Assets and liabilities denominated in foreign currencies are translated using exchange rates at the end of the period; revenues and expenses are translated at average monthly rates. Gains and losses on foreign currency translation are a component of accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Transaction gains and losses are recorded in other, net in the Consolidated Statements of Operations. The Company enters into foreign currency forward contracts to hedge its net investment in its U.K. subsidiaries. Gains and losses on these transactions are included in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition.
Revenue Recognition	Revenue Recognition The Company’s classification of revenues in the Consolidated Statements of Operations represents revenues from contracts with customers disaggregated by type of revenue. The Company has four revenue streams as described below. Commission Revenue. The Company charges its broker-dealer clients variable transaction fees for trades executed on its platform and, under certain plans, distribution fees or monthly minimum fees to use the platform for a particular product area. Variable transaction fees are recognized on a trade date basis and generally calculated as a percentage of the notional dollar volume of bonds traded on the platforms and vary based on the type, size, yield and maturity of the bond traded and individual client incentives. Bonds that are more actively traded or that have shorter maturities generally generate lower commissions, while bonds that are less actively traded or that have longer maturities generally command higher commissions. Under the Company’s disclosed trading transaction fee plans, variable transaction fees, distribution fees and unused monthly fee commitments are invoiced and recorded on a monthly basis. For Open Trading trades that the Company executes between and among institutional investor and broker-dealer clients on a matched principal basis by serving as counterparty to both the buyer and the seller, the Company earns its commission through the difference in price between the two trades. The commission is collected upon settlement of the trade, which typically occurs within one to two trading days after the trade date. For U.S. Treasury matched principal trades, commissions are invoiced and recorded on a monthly basis. The following table presents commission revenue by fee type: Year Ended December 31, 2020 2019 2018 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 343,427 $ 266,916 $ 228,004 Open Trading - matched principal trading 170,537 98,080 65,932 U.S. Treasuries - matched principal trading 12,372 2,184 — Total variable transaction fees 526,337 367,180 293,936 Distribution fees and unused minimum fees 108,108 96,676 96,898 Total commissions $ 634,445 $ 463,856 $ 390,834 Information services – Information services includes data licensed to the Company’s broker-dealer clients, institutional investor clients and data-only subscribers; professional and consulting services; technology software licenses; and maintenance and support services. The nature and timing of each performance obligation may vary as these contracts are either subscription-based services transferred over time, and may be net of volume-based discounts, or one-time services that are transferred at a point in time. Revenues for services transferred over time are recognized ratably over the contract period as the Company’s performance obligation is met whereas revenues for services transferred at a point in time are recognized in the period the services are provided. Customers are generally billed monthly, quarterly, or annually; revenues billed in advance are deferred and recognized ratably over the contract period. The following table presents information services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 32,425 $ 29,619 $ 27,475 Services transferred at a point in time 1,916 1,111 752 Total information services revenues $ 34,341 $ 30,730 $ 28,227 Post-trade services – Post-trade services revenue is generated from regulatory transaction reporting, trade publication and trade matching services. Customers are generally billed monthly in arrears and revenue is recognized in the period transactions are processed. Revenues billed in advance are deferred and recognized ratably over the contract period. The Company also generates one-time implementation fees for onboarding clients which are invoiced and recognized in the period the implementation is completed. The following table presents post-trade services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 19,158 $ 15,669 $ 15,013 Services transferred at a point in time 302 94 333 Total post-trade services revenues $ 19,460 $ 15,763 $ 15,346 Other revenues – Other revenues primarily includes revenue from telecommunications line charges to broker-dealer clients. Contract liabilities consist of deferred revenues that the Company records when cash payments are received or due in advance of services to be performed. The revenue recognized from contract liabilities and the remaining balance is shown below: December 31, 2019 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation December 31, 2020 (In thousands) Information services $ 2,138 $ 9,593 $ (8,528 ) $ — $ 3,203 Post-trade services 1,361 15,496 (15,862 ) 50 1,045 Total deferred revenue $ 3,499 $ 25,089 $ (24,390 ) $ 50 $ 4,248 The majority of the Company’s contracts are short-term in nature with durations of less than one-year. For contracts with original durations extending beyond one year, the aggregate amount of the transaction price allocated to remaining performance obligations was $21.1 million as of December 31, 2020. The Company expects to recognize revenue associated with the remaining performance obligations over the next 33 months.
Stock-Based Compensation	Stock-Based Compensation The Company measures and recognizes compensation expense for all share-based payment awards based on their estimated fair values measured as of the grant date. These costs are recognized as an expense in the Consolidated Statements of Operations over the requisite service period, which is typically the vesting period, with an offsetting increase to additional paid-in capital. Forfeitures are recognized as they occur.
Income Taxes	Income Taxes Income taxes are accounted for using the asset and liability method. Deferred income taxes reflect the net tax effects of temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when such differences are expected to reverse. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is recognized against deferred tax assets if it is more likely than not that such assets will not be realized in future years. The Company recognizes interest and penalties related to unrecognized tax benefits in the provision for income taxes in the Consolidated Statements of Operations. All tax effects related to share-based payments are recorded in the provision for income taxes in the periods during which the awards are exercised or vest.
Business Combinations, Goodwill and Intangible Assets	Business Combinations, Goodwill and Intangible Assets Business combinations are accounted for under the purchase method of accounting. The total cost of an acquisition is allocated to the underlying net assets based on their respective estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Determining the fair value of certain assets acquired and liabilities assumed is judgmental in nature and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth rates, customer attrition rates and asset lives. The Company operates as a single reporting unit. Following an acquisition, goodwill no longer retains its identification with a particular acquisition, but instead becomes identifiable with the entire reporting unit. As a result, all of the fair value of the Company is available to support the value of goodwill. An impairment review of goodwill is performed on an annual basis, at year-end, or more frequently if circumstances change. Intangible assets with definite lives, including purchased technologies, customer relationships and other intangible assets, are amortized over their estimated useful lives which range from one to 15 years using either a straight-line or accelerated amortization method based on the pattern of economic benefit the Company expects to realize from such assets. Intangible assets are assessed for impairment when events or circumstances indicate the existence of a possible impairment.
Earnings Per Share	Earnings Per Share Basic earnings per share is computed by dividing the net income attributable to common stock by the weighted-average number of shares of common stock outstanding during the period. For purposes of computing diluted earnings per share, the weighted-average shares outstanding of common stock reflects the dilutive effect that could occur if convertible securities or other contracts to issue common stock were converted into or exercised for common stock.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Commission Revenue by Fee Type	The following table presents commission revenue by fee type: Year Ended December 31, 2020 2019 2018 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 343,427 $ 266,916 $ 228,004 Open Trading - matched principal trading 170,537 98,080 65,932 U.S. Treasuries - matched principal trading 12,372 2,184 — Total variable transaction fees 526,337 367,180 293,936 Distribution fees and unused minimum fees 108,108 96,676 96,898 Total commissions $ 634,445 $ 463,856 $ 390,834
Summary of Information Services Revenue by Timing of Recognition	The following table presents information services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 32,425 $ 29,619 $ 27,475 Services transferred at a point in time 1,916 1,111 752 Total information services revenues $ 34,341 $ 30,730 $ 28,227
Summary of Post-Trade Services Revenue by Timing of Recognition	The following table presents post-trade services revenue by timing of recognition: Year Ended December 31, 2020 2019 2018 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 19,158 $ 15,669 $ 15,013 Services transferred at a point in time 302 94 333 Total post-trade services revenues $ 19,460 $ 15,763 $ 15,346
Summary of Revenue Recognized from Contract Liabilities and Remaining Balance	The revenue recognized from contract liabilities and the remaining balance is shown below: December 31, 2019 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation December 31, 2020 (In thousands) Information services $ 2,138 $ 9,593 $ (8,528 ) $ — $ 3,203 Post-trade services 1,361 15,496 (15,862 ) 50 1,045 Total deferred revenue $ 3,499 $ 25,089 $ (24,390 ) $ 50 $ 4,248

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Valuation of Company's Assets and Liabilities Measured at Fair Value	The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2: Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2020 Money market funds $ 20,856 $ — $ — $ 20,856 Trading securities Corporate debt — 19,222 — 19,222 Mutual funds held in rabbi trust — 8,889 — 8,889 Foreign currency forward position — (805 ) — (805 ) Total $ 20,856 $ 27,306 $ — $ 48,162 As of December 31, 2019 Money market funds $ 99,755 $ — $ — $ 99,755 Securities available-for-sale Corporate debt — 137,835 — 137,835 Trading securities Corporate debt — 31,120 — 31,120 U.S. Treasuries — 55,305 — 55,305 Mutual funds held in rabbi trust — 6,217 — 6,217 Foreign currency forward position — (2,772 ) — (2,772 ) Total $ 99,755 $ 227,705 $ — $ 327,460
Carrying Value of Financial Asset and Liability Not Measured at Fair Value	The table below presents the carrying value, fair value and fair value hierarchy category of the Company’s financial assets and liabilities that are not measured at fair value on the Consolidated Statement of Financial Condition. The carrying values of the Company’s financial assets and liabilities not measured at fair value categorized in the fair value hierarchy as Level 1 and Level 2 approximate fair value due to the short-term nature of the underlying assets and liabilities. Carrying Value Fair Value Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2020 Financial assets not measured at fair value: Cash and cash equivalents $ 460,858 $ 460,858 $ 460,858 $ — $ — $ 460,858 Cash segregated under federal regulations 50,059 50,059 50,059 — — 50,059 Accounts receivable, net of allowance 79,577 79,577 — 79,577 — 79,577 Receivables from broker-dealers, clearing organizations and customers 279,915 279,915 97,043 182,872 — 279,915 Total $ 870,409 $ 870,409 $ 607,960 $ 262,449 $ — $ 870,409 Financial liabilities not measured at fair value: Payables to broker-dealers, clearing organizations and customers $ 133,326 $ 133,326 $ — $ 133,326 $ — $ 133,326 As of December 31, 2019 Financial assets not measured at fair value: Cash and cash equivalents $ 270,124 $ 270,124 $ 270,124 $ — $ — $ 270,124 Accounts receivable, net of allowance 62,017 62,017 — 62,017 — 62,017 Total $ 332,141 $ 332,141 $ 270,124 $ 62,017 $ — $ 332,141
Summary of Foreign Currency Forward Contracts	A summary of the foreign currency forward position is as follows: As of December 31, 2020 2019 (In thousands) Notional value $ 157,057 $ 155,885 Fair value of notional 157,862 158,657 Fair value of the (liability) $ (805 ) $ (2,772 )
Summary of Company's Investments	The following is a summary of the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value (In thousands) As of December 31, 2020 Trading securities Corporate debt $ 19,081 $ 141 $ — $ 19,222 Mutual funds held in rabbi trust 7,680 1,209 — 8,889 Total investments $ 26,761 $ 1,350 $ — $ 28,111 As of December 31, 2019 Securities available-for-sale Corporate debt $ 137,119 $ 721 $ (5 ) $ 137,835 Trading securities Corporate debt 31,120 14 (14 ) 31,120 U.S. Treasuries 54,738 567 — 55,305 Mutual funds held in rabbi trust 5,173 1,044 — 6,217 Total trading securities 91,031 1,625 (14 ) 92,642 Total investments $ 228,150 $ 2,346 $ (19 ) $ 230,477
Summary of Fair Value of Investments Based upon Contractual Maturities	The following table summarizes the fair value of the investments based upon the contractual maturities: As of December 31, 2020 2019 (In thousands) Less than one year $ 18,290 $ 120,850 Due in 1 - 5 years 9,821 109,627 Total $ 28,111 $ 230,477
Fair Values and Unrealized Losses on Corporate Debt Investments	The following table provides fair values and unrealized losses on corporate debt investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2020 and 2019 respectively: Less than Twelve Months Twelve Months or More Total Fair value Gross unrealized losses Fair value Gross unrealized losses Fair value Gross unrealized losses (In thousands) As of December 31, 2020 Corporate debt $ 1,369 $ — $ — $ — $ — $ — As of December 31, 2019 Corporate debt $ 27,999 $ (18 ) $ 4,406 $ (1 ) $ 32,405 $ (19 )

Receivables from and Payables_2

Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Due To And From Broker Dealers And Clearing Organizations [Abstract]
Schedule of Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers	As of December 31, 2020, receivables from and payables to broker-dealers, clearing organizations and customers consisted of the following: December 31, 2020 Receivables from broker-dealers, clearing organizations and customers: (In thousands) Securities failed-to-deliver - broker-dealers $ 93,294 Securities failed-to-deliver - customers 87,685 Deposits with clearing organizations and broker-dealers 97,043 Other 1,893 Total $ 279,915 Payables to broker-dealers, clearing organizations and customers: Securities failed-to-receive - broker-dealers 70,917 Securities failed-to-receive - customers 60,784 Other 1,625 Total $ 133,326

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Summary of Purchase Price Allocation	The Company has completed an allocation of the purchase price to the fair value of assets acquired and liabilities assumed at the date of acquisition. The Company utilized an independent third-party to determine the fair value of the acquired intangible assets. The purchase price allocation is as follows (in thousands): Purchase price $ 153,210 Less: acquired cash (2,935 ) Purchase price, net of acquired cash 150,275 Accounts receivable (1,811 ) Intangible assets (58,780 ) Prepaid expenses and other assets (4,168 ) Accounts payable, accrued expenses and other liabilities 2,165 Goodwill $ 87,681
Summary of Acquired Intangible Assets and Useful Lives	The acquired intangible assets and useful lives are as follows ($ in thousands): Costs Useful Lives Customer relationships $ 58,690 15 years Tradename - finite life 90 1 year Total $ 58,780

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Company's Intangible Assets	Intangible assets that are subject to amortization, including the related accumulated amortization, are comprised of the following: December 31, 2020 December 31, 2019 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Technology $ 5,770 $ (5,770 ) $ — $ 5,770 $ (5,770 ) $ — Customer relationships 102,696 (7,369 ) 95,327 64,332 (3,451 ) 60,881 Non-competition agreements 380 (380 ) — 380 (380 ) — Tradenames and patents 400 (373 ) 27 490 (385 ) 105 Total $ 109,246 $ (13,892 ) $ 95,354 $ 70,972 $ (9,986 ) $ 60,986

Capitalized Software, Furnitu_2

Capitalized Software, Furniture, Equipment and Leasehold Improvements (Tables)	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Capitalized Software Development Costs, Furniture, Equipment and Leasehold Improvements, Net of Accumulated Depreciation and Amortization	Capitalized software development costs, furniture, equipment and leasehold improvements, net of accumulated depreciation and amortization, are comprised of the following: As of December 31, 2020 2019 (In thousands) Software development costs $ 151,139 $ 119,911 Computer hardware and related software 52,696 48,379 Office hardware 8,782 5,725 Furniture and fixtures 7,078 5,000 Leasehold improvements 29,064 27,966 248,759 206,981 Accumulated depreciation and amortization (163,555 ) (135,186 ) Total $ 85,204 $ 71,795

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Provision for Income Taxes	The provision for income taxes consists of the following: Year Ended December 31, 2020 2019 2018 (In thousands) Current: Federal $ 30,215 $ 28,928 $ 31,617 State and local 19,130 7,686 5,928 Foreign 15,538 13,234 8,862 Total current provision 64,883 49,848 46,407 Deferred: Federal 7,474 2,579 (1,416 ) State and local 1,439 403 (272 ) Foreign 1,186 (308 ) 515 Total deferred provision 10,099 2,674 (1,173 ) Provision for income taxes $ 74,982 $ 52,522 $ 45,234
Difference Between the Company's Reported Provision for Income Taxes and the U.S. Federal Statutory Rate	The difference between the Company’s reported provision for income taxes and the U.S. federal statutory rate of 21% is as follows: Year Ended December 31, 2020 2019 2018 U.S. federal tax at statutory rate 21.0 % 21.0 % 21.0 % State and local taxes - net of federal benefit 4.4 2.5 2.0 Credits and deductions related to research activities (0.3 ) (0.3 ) (0.3 ) Foreign rate differential benefit (0.4 ) (0.5 ) (0.5 ) Excess tax benefit from stock-based compensation (5.4 ) (3.5 ) (2.1 ) Other, net 0.7 1.2 0.6 Provision for income taxes 20.0 % 20.4 % 20.7 %
Summary of Company's Net Deferred Tax Assets	The following is a summary of the Company’s net deferred tax assets: As of December 31, 2020 2019 (In thousands) Deferred tax assets: Stock compensation expense $ 3,682 $ 4,926 Operating lease liabilities 19,339 20,227 Other 1,968 892 Total deferred tax assets 24,989 26,045 Valuation allowance — — Net deferred tax assets 24,989 26,045 Deferred tax liabilities: Depreciation and amortization (9,729 ) (4,085 ) Capitalized software development costs (7,828 ) (5,306 ) Goodwill and intangible assets (2,852 ) (1,120 ) Operating lease right-of-use assets (15,600 ) (16,515 ) Deferred tax (liability) asset, net $ (11,020 ) $ (981 )
Reconciliation of the Unrecognized Tax Benefits	A reconciliation of the unrecognized tax benefits is as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Balance at beginning of year $ 6,831 $ 4,718 $ 2,650 Additions attributable to state and local tax apportionment 9,486 2,113 2,068 Balance at end of year $ 16,317 $ 6,831 $ 4,718

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Summary of the Change in the Company's Outstanding Shares of Common Stock	The following is a summary of the change in the Company’s outstanding shares of voting common stock: Year Ended December 31, 2020 2019 2018 (In thousands) Outstanding shares of voting common stock at the beginning of year 37,936 37,640 37,621 Exercise of stock options 177 147 121 Issuance of restricted stock, net of cancellations 56 161 67 Shares withheld for withholding tax payments (125 ) (98 ) (45 ) Treasury shares used for acquisition — 146 — Repurchases (39 ) (60 ) (124 ) Outstanding shares of voting common stock at the end of year 38,005 37,936 37,640

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense	Total stock-based compensation expense was as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Employees: Restricted stock and performance shares $ 21,310 $ 20,182 $ 12,559 Stock options 3,100 4,032 2,193 24,410 24,214 14,752 Non-employee directors: Restricted stock 1,203 1,080 1,098 Total stock-based compensation $ 25,613 $ 25,294 $ 15,850
Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted	The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted, excluding the two awards discussed below: Year Ended December 31, 2020 2019 2018 Expected life (years) 5.0 5.0 5.0 Risk-free interest rate 1.6 % 2.6 % 2.2 % Expected volatility 26.8 % 25.9 % 26.9 % Expected dividend yield 0.6 % 0.8 % 0.8 %
Stock Option Activity	The following table reports stock option activity during the three years ended December 31, 2020 and the intrinsic value as of December 31, 2020: Number of Shares Weighted-Average Exercise Price ($) Remaining Contractual Term Intrinsic Value ($) (In thousands) Outstanding at December 31, 2017 529,611 67.60 Granted 168,217 261.19 Canceled (1,676 ) 142.69 Exercised (120,588 ) 24.66 Outstanding at December 31, 2018 575,564 132.93 Granted 82,474 279.57 Canceled (548 ) 198.67 Exercised (106,899 ) 28.24 Outstanding at December 31, 2019 550,591 175.16 Granted 13,900 368.10 Canceled (218 ) 307.52 Exercised (176,901 ) 84.07 76,709 Outstanding at December 31, 2020 387,372 223.60 2.8 134,401 Exercisable at December 31, 2020 99,415 137.78 1.7 43,025
Summary of Performance of Share Activity for Annual Awards	The following table reports performance share activity for the one-year performance awards for the two years ended December 31, 2019: Performance year: 2019 2018 Target share pay-out 16,716 10,479 Actual share pay-out (paid in following year) 19,401 10,479 Weighted average fair value per share on grant date $ 223.81 $ 202.04
Restricted Stock and Performance Share Activity	The following table reports restricted stock and performance share activity during the three years ended December 31, 2020: Number of Restricted Shares Weighted-Average Grant Date Fair Value Outstanding at December 31, 2017 319,599 $ 88.77 Granted 59,179 Performance share pay-out 8,094 Canceled (4,046 ) Vested (110,956 ) Outstanding at December 31, 2018 271,870 $ 112.47 Granted 118,632 Performance share pay-out 87,163 Canceled (2,321 ) Vested (129,312 ) Outstanding at December 31, 2019 346,032 $ 154.27 Granted 38,907 Performance share pay-out 19,401 Canceled (3,480 ) Vested (170,213 ) Outstanding at December 31, 2020 230,647 $ 224.63

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Basic and Diluted Weighted Average Shares Outstanding Used to Compute Earnings Per Share	The following table sets forth basic and diluted weighted average shares outstanding used to compute earnings per share: Year Ended December 31, 2020 2019 2018 (In thousands, except per share amounts) Basic weighted average shares outstanding 37,359 37,083 36,958 Dilutive effect of stock options and restricted stock 785 873 897 Diluted weighted average shares outstanding 38,144 37,956 37,855 Basic earnings per share $ 8.01 $ 5.53 $ 4.68 Diluted earnings per share $ 7.85 $ 5.40 $ 4.57

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Components of Occupancy Expense	The following table presents the components of occupancy expense for the years ended December 31, 2020 and 2019: Lease cost: Classification 2020 2019 (In thousands) Operating lease cost Occupancy $ 13,455 $ 10,875 Operating lease cost for subleased/assigned properties Other, net 2,404 2,422 Variable lease costs Occupancy 26 169 Sublease income for subleased/assigned properties Other, net (2,420 ) (2,422 ) Net lease cost $ 13,465 $ 11,044
Summary of Weighted Average Remaining Lease Term and Discount Rate	The weighted average remaining lease term and weighted average discount rate are as follows: As of December 31, Lease Term and Discount Rate 2020 2019 Weighted average remaining lease term (in years) 12.3 13.3 Weighted average discount rate 5.9 % 5.9 %
Schedule of Maturity of Lease Liabilities	The following table presents the maturity of lease liabilities as of December 31, 2020: (In thousands) 2021 $ 12,131 2022 10,516 2023 10,270 2024 10,937 2025 10,937 2026 and thereafter 79,003 Total lease payments 133,794 Less: interest 40,182 Present value of lease liabilities $ 93,612

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Summary of Revenue and Long-lived Assets	Revenues for the three years ended December 31, 2020, 2019 and 2018 and long-lived assets as of December 31, 2020 and 2019 were as follows: Year Ended December 31, 2020 2019 2018 (In thousands) Revenues Americas $ 583,164 $ 427,276 $ 369,324 Europe 89,751 74,511 59,943 Asia 16,210 9,565 6,298 Total $ 689,125 $ 511,352 $ 435,565 As of December 31, 2020 2019 (In thousands) Long-lived assets, as defined Americas $ 68,707 $ 62,376 Europe 16,491 9,410 Asia 6 9 Total $ 85,204 $ 71,795

Cash and Cash Equivalents and_2

Cash and Cash Equivalents and Restricted Cash (Tables)	12 Months Ended
	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash	The following table provides a reconciliation of cash and cash equivalents together with restricted or segregated cash as reported within the Consolidated Statements of Financial Condition to the sum of the same such amounts shown in the Consolidated Statements of Cash Flows: Statement of Financial Condition Location December 31, 2020 December 31, 2019 (In thousands) Cash and cash equivalents Cash and cash equivalents $ 460,858 $ 270,124 Cash segregated for regulatory purposes Cash segregated under federal regulations 50,059 — Deposits with clearing organizations and broker-dealers Receivables from broker-dealers, clearing organizations and customers 97,043 — Other deposits Prepaid expenses and other assets 90 4,129 Total $ 608,050 $ 274,253

Parent Company Information (Tab

Parent Company Information (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Condensed Statements of Financial Condition	MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Financial Condition As of December 31, 2020 December 31, 2019 (In thousands) ASSETS Cash and cash equivalents $ 55,747 $ 48,241 Investments, at fair value 4,811 141,318 Accounts receivable 178 63 Receivable from subsidiaries 41,986 5,997 Intangible assets, net of accumulated amortization 27 30 Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization 23,518 25,247 Operating lease right-of-use assets 64,460 68,559 Investments in subsidiaries 853,626 570,145 Prepaid expenses and other assets 4,591 6,978 Income and other tax receivable 9,028 3,219 Total assets $ 1,057,972 $ 869,797 LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities Accrued employee compensation $ 10,241 $ 6,543 Income and other tax liabilities 3,457 — Accounts payable, accrued expenses and other liabilities 9,341 9,254 Operating lease liabilities 79,872 83,909 Total liabilities 102,911 99,706 Stockholders' equity Preferred stock — — Series A Preferred Stock — — Common stock voting 123 122 Common stock non-voting — — Additional paid-in capital 329,742 342,541 Treasury stock (169,523 ) (153,388 ) Retained earnings 799,369 591,086 Accumulated other comprehensive loss (4,650 ) (10,270 ) Total stockholders' equity 955,061 770,091 Total liabilities and stockholders' equity $ 1,057,972 $ 869,797
Condensed Statements of Operations and Comprehensive Income	MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Operations and Comprehensive Income Year Ended December 31, 2020 2019 2018 (In thousands) Dividends from subsidiary $ 30,000 $ 165,000 $ 130,000 Expenses Employee compensation and benefits 19,710 16,100 10,785 Depreciation and amortization 2,068 1,919 1,760 Technology and communications 10 13 43 Professional and consulting fees 7,332 6,523 4,932 Occupancy 162 850 7,381 General and administrative 2,551 2,252 1,513 Total expenses 31,833 27,657 26,414 Operating (loss) income (1,833 ) 137,343 103,586 Other income (expense) Investment income 2,799 5,305 3,835 Interest expense (805 ) — — Other, net (318 ) (1,344 ) (711 ) Total other income 1,676 3,961 3,124 (Loss) income before income taxes and equity in undistributed earnings of subsidiaries (157 ) 141,304 106,710 Provision for income taxes (23,444 ) (9,442 ) (7,350 ) Income before equity in undistributed income of subsidiaries 23,287 150,746 114,060 Equity in undistributed income of subsidiaries 276,090 54,156 58,792 Net income 299,377 204,902 172,852 Other comprehensive income (loss), net 5,620 2,124 (2,168 ) Comprehensive income $ 304,997 $ 207,026 $ 170,684
Condensed Statements of Cash Flows	MarketAxess Holdings Inc. (Parent Company Only) Condensed Statements of Cash Flows Year Ended December 31, 2020 2019 2018 (In thousands) Cash flows from operating activities Net income $ 299,377 $ 204,902 $ 172,852 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 2,068 1,919 1,760 Amortization of operating lease right-of-use assets 4,117 4,027 — Stock-based compensation expense 10,834 10,547 5,801 Deferred taxes 3,644 1,255 (2,515 ) Equity in undistributed income of subsidiaries (276,090 ) (54,156 ) (58,792 ) Other (671 ) 328 710 Changes in operating assets and liabilities: (Increase) in accounts receivable (115 ) (4 ) (14 ) (Increase) decrease in receivable from subsidiaries (25,049 ) 5,253 15,985 (Increase) decrease in prepaid expenses and other assets (1,085 ) 933 (782 ) (Increase) in mutual funds held in rabbi trust (1,328 ) (1,183 ) (470 ) Increase in accrued employee compensation 3,698 876 567 (Increase) in income and other tax receivable (1,240 ) (3,219 ) — Increase (decrease) in income and other tax liabilities 6,676 (2,612 ) 469 (Decrease) increase in accounts payable, accrued expenses and other liabilities (442 ) (2,039 ) 13,619 (Decrease) increase in operating lease liabilities (4,055 ) 1,191 — Net cash provided by operating activities 20,339 168,018 149,190 Cash flows from investing activities Acquisition of business, net of cash and cash equivalents acquired — (102,320 ) — Available-for-sale investments Proceeds from maturities and sales 170,657 170,936 333,791 Purchases (32,865 ) (160,827 ) (336,533 ) Purchases of furniture, equipment and leasehold improvements (337 ) (1,424 ) (24,786 ) Purchase of intangible asset — (30 ) — Net cash provided by (used in) investing activities 137,455 (93,665 ) (27,528 ) Cash flows from financing activities Cash dividend on common stock (90,566 ) (76,231 ) (62,432 ) Exercise of stock options 4,007 1,207 2,973 Withholding tax payments on restricted stock vesting and stock option exercises (42,418 ) (25,820 ) (8,043 ) Repurchases of common stock (16,135 ) (17,256 ) (25,171 ) Proceeds from short-term borrowings 348,000 — — Repayments of short-term borrowings (348,000 ) — — Net cash (used in) financing activities (145,112 ) (118,100 ) (92,673 ) Effect of exchange rate changes on investments (5,176 ) (3,852 ) 4,129 Cash and cash equivalents including restricted cash Net increase (decrease) for the period 7,506 (47,599 ) 33,118 Beginning of period 48,241 95,840 62,722 End of period $ 55,747 $ 48,241 $ 95,840 Supplemental cash flow information: Cash paid for income taxes $ 32,674 $ 41,025 $ 37,721 Cash paid for interest 805 — — Non-cash investing and financing activity: Exercise of stock options - cashless $ 10,866 $ 1,811 $ — Treasury stock used for acquisition of business — (48,830 ) —

Organization and Principal Bu_2

Organization and Principal Business Activity - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020Institutional_Investor_and_Broker-dealer_Firm
Accounting Policies [Line Items]
Date of incorporation	Apr. 11, 2000
Minimum [Member]
Accounting Policies [Line Items]
Number of institutional investor and broker-dealer firms	1,800

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)Revenue	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Significant Accounting Policies [Line Items]
Maximum maturity period for classification of investments as cash equivalents	3 months
Investments other-than-temporary losses	$ 0	$ 0	$ 0
Allowance for credit losses	163,000	57,000	100,000
Provision for bad debts	500,000	300,000	200,000
Write-offs and other charges against the allowance for credit losses	$ 100,000	$ 100,000	$ 200,000
Number of revenue streams | Revenue	4
Description of commission revenue	For Open Trading trades that the Company executes between and among institutional investor and broker-dealer clients on a matched principal basis by serving as counterparty to both the buyer and the seller, the Company earns its commission through the difference in price between the two trades.
Settlement days of bond transaction	within one to two trading days
Maximum [Member]
Significant Accounting Policies [Line Items]
Contractual maturities accounts receivable	1 year
Estimated useful life of fixed assets	7 years
Maximum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	15 years
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life of fixed assets	3 years
Minimum [Member] | Business Combinations [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	1 year
Minimum [Member] | Internally Developed Software [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	3 years
ASU 2018-15 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jul. 1, 2019
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	false
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2017-04 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	false
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
ASU 2016-13 [Member]
Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Retrospective Application Impracticable [true false]	true
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Commission Revenue by Fee Type (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Commission revenue by fee type
Revenues	$ 689,125	$ 511,352	$ 435,565
Commissions [Member]
Commission revenue by fee type
Disclosed trading	343,427	266,916	228,004
Matched principal trading	170,537	98,080	65,932
Total variable transaction fees	526,337	367,180	293,936
Distribution fees and unused minimum fees	108,108	96,676	96,898
Revenues	634,445	463,856	$ 390,834
Commissions [Member] | U.S. Treasuries [Member]
Commission revenue by fee type
Matched principal trading	$ 12,372	$ 2,184

Significant Accounting Polici_6

Significant Accounting Policies - Summary of Information Services Revenue by Timing of Recognition (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Revenues	$ 689,125	$ 511,352	$ 435,565
Information Services [Member]
Significant Accounting Policies [Line Items]
Revenues	34,341	30,730	28,227
Information Services [Member] | Transferred over Time [Member]
Significant Accounting Policies [Line Items]
Revenues	32,425	29,619	27,475
Information Services [Member] | Transferred at a Point in Time [Member]
Significant Accounting Policies [Line Items]
Revenues	$ 1,916	$ 1,111	$ 752

Significant Accounting Polici_7

Significant Accounting Policies - Summary of Post-Trade Services Revenue by Timing of Recognition (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Revenues	$ 689,125	$ 511,352	$ 435,565
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Revenues	19,460	15,763	15,346
Post-trade Services [Member] | Transferred over Time [Member]
Significant Accounting Policies [Line Items]
Revenues	19,158	15,669	15,013
Post-trade Services [Member] | Transferred at a Point in Time [Member]
Significant Accounting Policies [Line Items]
Revenues	$ 302	$ 94	$ 333

Significant Accounting Polici_8

Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 3,499
Payments received in advance of services to be performed	25,089
Revenue recognized for services performed during the period	(24,390)
Foreign Currency Translation	50
Deferred revenues, ending balance	4,248
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	2,138
Payments received in advance of services to be performed	9,593
Revenue recognized for services performed during the period	(8,528)
Deferred revenues, ending balance	3,203
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,361
Payments received in advance of services to be performed	15,496
Revenue recognized for services performed during the period	(15,862)
Foreign Currency Translation	50
Deferred revenues, ending balance	$ 1,045

Significant Accounting Polici_9

Significant Accounting Policies - Additional Information (Detail 1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01 $ in Millions	Dec. 31, 2020USD ($)
Significant Accounting Policies [Line Items]
Aggregate amount of transaction price allocated to remaining performance obligations	$ 21.1
Expected time to recognize revenue for remaining performance obligation	33 months

Regulatory Capital Requiremen_2

Regulatory Capital Requirements - Additional Information (Detail) $ in Millions	Dec. 31, 2020USD ($)
Brokers And Dealers [Abstract]
Aggregate net capital and financial resources in excess of required level	$ 435.4
Aggregate net capital and financial resources, minimum capital requirement	21.6
Securities reserve deposit	$ 50.1

Fair Value Measurements - Valua

Fair Value Measurements - Valuation of Company's Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	$ 20,856	$ 99,755
Trading securities		92,642
Assets Fair Value Total	48,162	327,460
Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	19,222	31,120
Securities available-for-sale		137,835
Mutual Funds Held In Rabbi Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	8,889	6,217
U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities		55,305
Foreign Currency Forward Position [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	(805)	(2,772)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	20,856	99,755
Assets Fair Value Total	20,856	99,755
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Fair Value Total	27,306	227,705
Level 2 [Member] | Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	19,222	31,120
Securities available-for-sale		137,835
Level 2 [Member] | Mutual Funds Held In Rabbi Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	8,889	6,217
Level 2 [Member] | U.S. Treasuries [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities		55,305
Level 2 [Member] | Foreign Currency Forward Position [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	$ (805)	$ (2,772)

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Value of Financial Asset and Liability Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets not measured at fair value:
Financial assets not measured at fair value	$ 48,162	$ 327,460
Level 1 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	20,856	99,755
Level 2 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	27,306	227,705
Financial Assets and Liabilities not Measured [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	870,409	332,141
Financial Assets and Liabilities not Measured [Member] | Payables to Broker-Dealers, Clearing Organizations and Customers [Member]
Financial liabilities not measured at fair value:
Financial liabilities not measured at fair value	133,326
Financial Assets and Liabilities not Measured [Member] | Cash and Cash Equivalents [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	460,858	270,124
Financial Assets and Liabilities not Measured [Member] | Cash Segregated under Federal Regulations [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	50,059
Financial Assets and Liabilities not Measured [Member] | Accounts Receivable, Net of Allowance [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	79,577	62,017
Financial Assets and Liabilities not Measured [Member] | Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	279,915
Financial Assets and Liabilities not Measured [Member] | Level 1 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	607,960	270,124
Financial Assets and Liabilities not Measured [Member] | Level 1 [Member] | Cash and Cash Equivalents [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	460,858	270,124
Financial Assets and Liabilities not Measured [Member] | Level 1 [Member] | Cash Segregated under Federal Regulations [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	50,059
Financial Assets and Liabilities not Measured [Member] | Level 1 [Member] | Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	97,043
Financial Assets and Liabilities not Measured [Member] | Level 2 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	262,449	62,017
Financial Assets and Liabilities not Measured [Member] | Level 2 [Member] | Payables to Broker-Dealers, Clearing Organizations and Customers [Member]
Financial liabilities not measured at fair value:
Financial liabilities not measured at fair value	133,326
Financial Assets and Liabilities not Measured [Member] | Level 2 [Member] | Accounts Receivable, Net of Allowance [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	79,577	62,017
Financial Assets and Liabilities not Measured [Member] | Level 2 [Member] | Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	182,872
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	870,409	332,141
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member] | Payables to Broker-Dealers, Clearing Organizations and Customers [Member]
Financial liabilities not measured at fair value:
Financial liabilities not measured at fair value	133,326
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member] | Cash and Cash Equivalents [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	460,858	270,124
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member] | Cash Segregated under Federal Regulations [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	50,059
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member] | Accounts Receivable, Net of Allowance [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	79,577	62,017
Financial Assets and Liabilities not Measured [Member] | Carrying Value [Member] | Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	279,915
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	870,409	332,141
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member] | Payables to Broker-Dealers, Clearing Organizations and Customers [Member]
Financial liabilities not measured at fair value:
Financial liabilities not measured at fair value	133,326
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member] | Cash and Cash Equivalents [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	460,858	270,124
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member] | Cash Segregated under Federal Regulations [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	50,059
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member] | Accounts Receivable, Net of Allowance [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	79,577	$ 62,017
Financial Assets and Liabilities not Measured [Member] | Fair Value [Member] | Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	$ 279,915

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Hedge derivative expiration period	1 month
Proceeds from the sales and maturities of securities available-for-sale	$ 261.6	$ 262.1	$ 409.3
Net unrealized (losses) gains on trading securities	(0.4)	$ 0.8
Net realized gains	$ 1.7

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Foreign Currency Forward Contracts (Detail) - Foreign Currency Forward Position [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives Fair Value [Line Items]
Notional value	$ 157,057	$ 155,885
Fair value of notional	157,862	158,657
Fair value of the (liability)	$ (805)	$ (2,772)

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Company's Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost		$ 91,031
Trading securities, Gross unrealized gains		1,625
Trading securities, Gross unrealized losses		(14)
Trading securities, Estimated fair value		92,642
Investments, Amortized cost	$ 26,761	228,150
Investments, Gross unrealized gains	1,350	2,346
Investments, Gross unrealized losses		(19)
Investments, Estimated fair value	28,111	230,477
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available-for-sale, Amortized cost		137,119
Securities available-for-sale, Gross unrealized gains		721
Securities available-for-sale, Gross unrealized losses		(5)
Securities available-for-sale, Estimated fair value		137,835
Trading securities, Amortized cost	19,081	31,120
Trading securities, Gross unrealized gains	141	14
Trading securities, Gross unrealized losses		(14)
Trading securities, Estimated fair value	19,222	31,120
U.S. Treasuries [Member]
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost		54,738
Trading securities, Gross unrealized gains		567
Trading securities, Estimated fair value		55,305
Mutual Funds Held In Rabbi Trust [Member]
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	7,680	5,173
Trading securities, Gross unrealized gains	1,209	1,044
Trading securities, Estimated fair value	$ 8,889	$ 6,217

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Fair Value of Investments Based upon Contractual Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Less than one year	$ 18,290	$ 120,850
Due in 1 - 5 years	9,821	109,627
Total	$ 28,111	$ 230,477

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values and Unrealized Losses on Corporate Debt Investments (Detail) - Corporate Debt [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Fair value	$ 1,369	$ 27,999
Less than Twelve Months, Gross unrealized losses		(18)
Twelve Months or More, Fair value		4,406
Twelve Months or More, Gross unrealized losses		(1)
Fair value, Total		32,405
Gross unrealized losses, Total		$ (19)

Receivables from and Payables_3

Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers - Schedule of Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers	$ 93,294
Securities failed-to-deliver - customers	87,685
Deposits with clearing organizations and broker-dealers	97,043
Other	1,893
Total	279,915
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers	70,917
Securities failed-to-receive - customers	60,784
Other	1,625
Total	$ 133,326

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands	Nov. 30, 2020	Nov. 01, 2019	Sep. 30, 2020
LiquidityEdge LLC [Member]
Business Acquisition [Line Items]
Aggregate consideration		$ 153,210
Cash consideration		$ 104,400
Business combination, shares of common stock		146,450
Business combination, common stock value		$ 48,800
Business combination, period for shares of common stock placed in escrow		18 months
Business combination, shares of common stock received period		6 months
Amortizable intangible assets		$ 58,780
Regulatory Services GmbH of Deutsche Borse Group [Member]
Business Acquisition [Line Items]
Cash consideration	$ 22,500
Amortizable intangible assets	$ 37,400
Business combination, contingent consideration payment period	18 months
Regulatory Services GmbH of Deutsche Borse Group [Member] | Maximum [Member]
Business Acquisition [Line Items]
Contingent consideration payable	$ 24,600
MuniBrokers LLC [Member]
Business Acquisition [Line Items]
Cash consideration			$ 45,000
Business combination, contingent consideration payment period			3 years
Transaction costs			$ 20,000
MuniBrokers LLC [Member] | Maximum [Member]
Business Acquisition [Line Items]
Contingent consideration payable			$ 25,000
Escrow [Member] | LiquidityEdge LLC [Member]
Business Acquisition [Line Items]
Business combination, shares of common stock		43,937

Acquisitions - Summary of Preli

Acquisitions - Summary of Preliminary Purchase Price Allocation (Detail) - USD ($) $ in Thousands	Nov. 01, 2019	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Goodwill		$ 147,388	$ 146,861
LiquidityEdge LLC [Member]
Business Acquisition [Line Items]
Purchase price	$ 153,210
Less: acquired cash	(2,935)
Purchase price, net of acquired cash	150,275
Accounts receivable	(1,811)
Intangible assets	(58,780)
Prepaid expenses and other assets	(4,168)
Accounts payable, accrued expenses and other liabilities	2,165
Goodwill	$ 87,681

Acquisitions - Summary of Acqui

Acquisitions - Summary of Acquired Intangible Assets and Useful Lives (Detail) - LiquidityEdge LLC [Member] $ in Thousands	Nov. 01, 2019USD ($)
Acquired Finite Lived Intangible Assets [Line Items]
Costs	$ 58,780
Customer Relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Costs	$ 58,690
Useful Lives	15 years
Tradename - Finite Life [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Costs	$ 90
Useful Lives	1 year

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Amortization expense associated with identifiable intangible assets	$ 3.9	$ 0.8	$ 0.4
Estimated total amortization expense 2021	5.7
Estimated total amortization expense 2022	6.9
Estimated total amortization expense 2023	7.9
Estimated total amortization expense 2024	6.7
Estimated total amortization expense 2025	5.7
Indefinite-lived Intangible Assets [Member]
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 147.4	$ 146.9

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Summary of Company's Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Cost	$ 109,246	$ 70,972
Accumulated amortization	(13,892)	(9,986)
Net carrying amount	95,354	60,986
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Cost	5,770	5,770
Accumulated amortization	(5,770)	(5,770)
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Cost	102,696	64,332
Accumulated amortization	(7,369)	(3,451)
Net carrying amount	95,327	60,881
Non-Competition Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Cost	380	380
Accumulated amortization	(380)	(380)
Tradenames and Patents [Member]
Finite Lived Intangible Assets [Line Items]
Cost	400	490
Accumulated amortization	(373)	(385)
Net carrying amount	$ 27	$ 105

Capitalized Software, Furnitu_3

Capitalized Software, Furniture, Equipment and Leasehold Improvements - Capitalized Software Development Costs, Furniture, Equipment and Leasehold Improvements, Net of Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 248,759	$ 206,981
Accumulated depreciation and amortization	(163,555)	(135,186)
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	85,204	71,795
Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	151,139	119,911
Computer Hardware and Related Software [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	52,696	48,379
Office Hardware [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	8,782	5,725
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	7,078	5,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 29,064	$ 27,966

Capitalized Software, Furnitu_4

Capitalized Software, Furniture, Equipment and Leasehold Improvements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Software development costs	$ 30.6	$ 22.4

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current:
Federal	$ 30,215	$ 28,928	$ 31,617
State and local	19,130	7,686	5,928
Foreign	15,538	13,234	8,862
Total current provision	64,883	49,848	46,407
Deferred:
Federal	7,474	2,579	(1,416)
State and local	1,439	403	(272)
Foreign	1,186	(308)	515
Total deferred provision	10,099	2,674	(1,173)
Provision for income taxes	$ 74,982	$ 52,522	$ 45,234

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Pre Tax Income [Line Items]
Pre-tax income from U.S. operations	$ 288,300	$ 190,400	$ 168,500
U.S. federal tax at statutory rate	21.00%	21.00%	21.00%
Unrecognized tax benefits	$ 16,317	$ 6,831	$ 4,718	$ 2,650
Recognized penalties and interest on unrecognized tax benefits	3,700	600	400
Penalties and interest accrued on unrecognized tax benefits	$ 4,900	1,200
New York State [Member] | Earliest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination	2010
New York State [Member] | Latest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination	2017
New York City [Member] | Earliest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination	2016
New York City [Member] | Latest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination	2018
Foreign Country [Member]
Schedule Of Pre Tax Income [Line Items]
Pre-tax income from foreign operations	$ 86,100	$ 67,000	$ 49,600

Income Taxes - Difference Betwe

Income Taxes - Difference Between the Company's Reported Provision for Income Taxes and the U.S. Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S. federal tax at statutory rate	21.00%	21.00%	21.00%
State and local taxes - net of federal benefit	4.40%	2.50%	2.00%
Credits and deductions related to research activities	(0.30%)	(0.30%)	(0.30%)
Foreign rate differential benefit	(0.40%)	(0.50%)	(0.50%)
Excess tax benefit from stock-based compensation	(5.40%)	(3.50%)	(2.10%)
Other, net	0.70%	1.20%	0.60%
Provision for income taxes	20.00%	20.40%	20.70%

Income Taxes - Summary of Compa

Income Taxes - Summary of Company's Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Stock compensation expense	$ 3,682	$ 4,926
Operating lease liabilities	19,339	20,227
Other	1,968	892
Total deferred tax assets	24,989	26,045
Net deferred tax assets	24,989	26,045
Deferred tax liabilities:
Depreciation and amortization	(9,729)	(4,085)
Capitalized software development costs	(7,828)	(5,306)
Goodwill and intangible assets	(2,852)	(1,120)
Operating lease right-of-use assets	(15,600)	(16,515)
Deferred tax (liability), net	$ (11,020)	$ (981)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 6,831	$ 4,718	$ 2,650
Additions attributable to state and local tax apportionment	9,486	2,113	2,068
Balance at end of year	$ 16,317	$ 6,831	$ 4,718

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended												12 Months Ended
	Jan. 31, 2021	Jan. 31, 2019	Sep. 30, 2017	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares authorized				110,000,000				110,000,000								110,000,000	110,000,000
Common stock entitles																one
Cash dividends declared per common share				$ 0.60	$ 0.60	$ 0.60	$ 0.60	$ 0.51	$ 0.51	$ 0.51	$ 0.51	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 2.40	$ 2.04	$ 1.68
Share Repurchase Program [Member]
Class of Stock [Line Items]
Shares repurchase program period		2 years	15 months
Shares repurchase program authorized		$ 100,000,000	$ 100,000,000
Commencement date		2019-04	2017-10
Share Repurchase Program [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Shares repurchase program authorized	$ 100,000,000
Commencement date	2021-04
Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized				10,000,000				10,000,000								10,000,000	10,000,000
Common Stock Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized				110,000,000				110,000,000								110,000,000	110,000,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of the Companys Change in the Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,935,984
Exercise of stock options	176,901	106,899	120,588
Outstanding shares of voting common stock at the end of year	38,005,330	37,935,984
Voting Common Stock [Member]
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,936,000	37,640,000	37,621,000
Exercise of stock options	177,000	147,000	121,000
Issuance of restricted stock, net of cancellations	56,000	161,000	67,000
Shares withheld for withholding tax payments	(125,000)	(98,000)	(45,000)
Treasury shares used for acquisition		146,000
Repurchases	(39,000)	(60,000)	(124,000)
Outstanding shares of voting common stock at the end of year	38,005,000	37,936,000	37,640,000

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Additional Information (Detail) - USD ($)	1 Months Ended			12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Nov. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant under the stock incentive plans				2,531,199
Weighted-average fair value option granted				$ 91.43	$ 58.37	$ 56.11
Number of awards excluded from option-pricing model				2
Grant date fair value				$ 76,709,000
Fair value assumptions, Dividend yield rate				0.60%	0.80%	0.80%
Closing price of common stock				$ 570.56
Unrecognized compensation costs related to non-vested				$ 5,900,000
Weighted-average period over which cost is expected to be recognized				2 years 4 months 24 days
Pay-out ranges, Minimum				0.00%
Pay-out ranges, Maximum				150.00%
Grant date deemed probable to vest				$ 43,025,000
Incentive Stock Options [Member] | President and Chief Operating Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock option equity instruments granted during the period		76,868
Grant date fair value		$ 2,900,000
Share-based compensation arrangement by share-based payment award award vesting date		Jan. 22, 2024
Fair value assumptions, Risk free interest rate		2.60%
Fair value assumptions, Volatility rate		25.80%
Fair value assumptions, Dividend yield rate		0.80%
Share-based compensation arrangement by share-based payment award, options expiry date		Jul. 22, 2024
Incentive Stock Options [Member] | President and Chief Operating Officer [Member] | Range One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value option granted		$ 272.88
Number of stock option equity instruments granted during the period		35,679
Percentage of fair market value of the common stock on the grant date		125.00%
Incentive Stock Options [Member] | President and Chief Operating Officer [Member] | Range Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value option granted		$ 294.71
Number of stock option equity instruments granted during the period		41,189
Percentage of fair market value of the common stock on the grant date		135.00%
Incentive Stock Options [Member] | Chief Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of stock option equity instruments granted during the period			148,524
Grant date fair value			$ 5,500,000
Share-based compensation arrangement by share-based payment award award vesting date			Nov. 8, 2023
Fair value assumptions, Risk free interest rate			3.10%
Fair value assumptions, Volatility rate			25.90%
Fair value assumptions, Dividend yield rate			0.80%
Share-based compensation arrangement by share-based payment award, options expiry date			May 8, 2024
Incentive Stock Options [Member] | Chief Executive Officer [Member] | Range One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value option granted			$ 257.78
Number of stock option equity instruments granted during the period			69,113
Percentage of fair market value of the common stock on the grant date			125.00%
Incentive Stock Options [Member] | Chief Executive Officer [Member] | Range Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value option granted			$ 278.40
Number of stock option equity instruments granted during the period			79,411
Percentage of fair market value of the common stock on the grant date			135.00%
Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested				$ 27,000,000
Weighted-average period over which cost is expected to be recognized				1 year 6 months
Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value	$ 368,100
Pay-out ranges, Minimum	0.00%
Pay-out ranges, Maximum	15000.00%
Performance period	3 years
Number of non-option equity instruments granted during the period	13,295
Grant date deemed probable to vest		$ 15,319,000
Performance Based Share [Member] | Chief Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value			$ 5,500,000
Share-based compensation arrangement by share-based payment award award vesting date			Nov. 8, 2023
Fair value assumptions, Risk free interest rate			3.10%
Fair value assumptions, Volatility rate			26.10%
Fair value assumptions, Dividend yield rate			0.80%
Performance period			5 years
Number of non-option equity instruments granted during the period			37,742
Performance Based Share [Member] | Chief Executive Officer [Member] | Range One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period			17,942
Fair value per share on the grant date			$ 257.78
Percentage of fair market value of the common stock on the grant date			125.00%
Performance Based Share [Member] | Chief Executive Officer [Member] | Range Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period			19,800
Fair value per share on the grant date			$ 278.40
Percentage of fair market value of the common stock on the grant date			135.00%
Performance Based Share [Member] | Chief Operating Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value		$ 2,900,000
Share-based compensation arrangement by share-based payment award award vesting date		Jan. 22, 2024
Fair value assumptions, Risk free interest rate		2.60%
Fair value assumptions, Volatility rate		25.90%
Fair value assumptions, Dividend yield rate		0.80%
Performance period		5 years
Number of non-option equity instruments granted during the period		18,914
Performance Based Share [Member] | Chief Operating Officer [Member] | Range One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period		8,969
Fair value per share on the grant date		$ 272.88
Percentage of fair market value of the common stock on the grant date		125.00%
Performance Based Share [Member] | Chief Operating Officer [Member] | Range Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period		9,945
Fair value per share on the grant date		$ 294.71
Percentage of fair market value of the common stock on the grant date		135.00%
Employees Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				1 year
Number of non-option equity instruments granted during the period				729	617	989
Percentage of shares grant to participants				20.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				3 years
Options Expiration Period				6 years
Minimum [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				3 years
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				5 years
Options Expiration Period				10 years
Maximum [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				5 years

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 24,410	$ 24,214	$ 14,752
Employees [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	21,310	20,182	12,559
Employees [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	3,100	4,032	2,193
Non-Employee Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	25,613	25,294	15,850
Non-Employee Directors [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 1,203	$ 1,080	$ 1,098

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans - Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected life (years)	5 years	5 years	5 years
Risk-free interest rate	1.60%	2.60%	2.20%
Expected volatility	26.80%	25.90%	26.90%
Expected dividend yield	0.60%	0.80%	0.80%

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	550,591	575,564	529,611
Number of Shares, Granted	13,900	82,474	168,217
Number of Shares, Canceled	(218)	(548)	(1,676)
Number of Shares, Exercised	(176,901)	(106,899)	(120,588)
Number of Shares, Ending Balance	387,372	550,591	575,564
Number of Shares, Exercisable	99,415
Weighted Average Exercise Price, Beginning Balance	$ 175.16	$ 132.93	$ 67.60
Weighted Average Exercise Price, Granted	368.10	279.57	261.19
Weighted Average Exercise Price, Canceled	307.52	198.67	142.69
Weighted Average Exercise Price, Exercised	84.07	28.24	24.66
Weighted Average Exercise Price, Ending Balance	223.60	$ 175.16	$ 132.93
Weighted Average Exercise Price, Exercisable	$ 137.78
Remaining Contractual Term, Outstanding at December 31, 2019	2 years 9 months 18 days
Remaining Contractual Term, Exercisable at December 31, 2020	1 year 8 months 12 days
Intrinsic Value, Exercised	$ 76,709
Intrinsic Value, Ending Balance	134,401
Intrinsic Value, Exercisable	$ 43,025

Stock-Based Compensation Plan_6

Stock-Based Compensation Plans - Summary of Performance of Share Activity for Annual Awards (Detail) - Performance Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Target share pay-out	16,716	10,479
Actual share pay-out (paid in following year)	19,401	10,479
Weighted average fair value per share on grant date	$ 223.81	$ 202.04

Stock-Based Compensation Plan_7

Stock-Based Compensation Plans - Restricted Stock and Performance Share Activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Shares, Beginning balance	346,032	271,870	319,599
Number of Restricted Shares, Granted	38,907	118,632	59,179
Number of Restricted Shares, Performance share pay-out	19,401	87,163	8,094
Number of Restricted Shares, Canceled	(3,480)	(2,321)	(4,046)
Number of Restricted Shares, Vested	(170,213)	(129,312)	(110,956)
Number of Restricted Shares, Ending balance	230,647	346,032	271,870
Weighted Average Grant Date Fair Value, Beginning balance	$ 154.27	$ 112.47	$ 88.77
Weighted Average Grant Date Fair Value, Ending balance	$ 224.63	$ 154.27	$ 112.47

Earnings Per Share - Basic and

Earnings Per Share - Basic and Diluted Weighted Average Shares Outstanding Used to Compute Earnings Per Share (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share Basic And Diluted [Abstract]
Basic weighted average shares outstanding	37,359	37,083	36,958
Dilutive effect of stock options and restricted stock	785	873	897
Diluted weighted average shares outstanding	38,144	37,956	37,855
Basic earnings per share	$ 8.01	$ 5.53	$ 4.68
Diluted earnings per share	$ 7.85	$ 5.40	$ 4.57

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Options and Restricted Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options and restricted stock excluded from the computation of diluted earnings per share	21,127	146,822	83,718

Credit Agreement - Additional I

Credit Agreement - Additional Information (Detail)	Nov. 13, 2020	Nov. 30, 2020USD ($)Extension_Option	Oct. 31, 2015USD ($)	Dec. 31, 2020USD ($)	Aug. 19, 2020USD ($)
Collateralized Agreement [Member]
Line Of Credit Facility [Line Items]
Interest expense on borrowings				$ 100,000
Maximum available borrowings to subsidiary under agreement				200,000,000
Outstanding borrowings under agreement				0
Unused borrowing capacity, amount under agreement				$ 200,000,000
Collateralized Agreement [Member] | Base Rate [Member]
Line Of Credit Facility [Line Items]
Interest rate, stated percentage				1.00%
Prior Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Revolving loans and letters of credit			$ 100,000,000	$ 450,000	$ 100,000
Expiration period of credit agreement				Nov. 30, 2020
Period of credit agreement	1 year		2 years
Maximum permitted investments and loans in broker dealer subsidiary				$ 500,000
Revolving Credit Facility [Member]
Line Of Credit Facility [Line Items]
Revolving loans and letters of credit		$ 500,000,000
Expiration period of credit agreement		Nov. 12, 2021
Period of credit agreement		364 days
Number of additional option to extend maturity date | Extension_Option		2
Letter of credit outstanding				1,000,000
Amount available under credit agreement				499,000,000
Additional borrowings under credit agreement				250,000,000
Interest expense on borrowings				$ 800,000
Standby Letters of Credit [Member]
Line Of Credit Facility [Line Items]
Sub-limit for letter of credit		$ 5,000,000

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Agreement
Lessee Lease Description [Line Items]
Operating lease, option to extend	Certain leases contain options to extend the initial term at the Company’s discretion
Operating lease, existence of option to extend [true false]	true
Number of sublease or lease agreements assigned to third parties | Agreement	2
Future lease obligation under sublease arrangements | $	$ 2.1
Property One [Member]
Lessee Lease Description [Line Items]
Lease termination dates	2022-02
Property Two [Member]
Lessee Lease Description [Line Items]
Lease termination dates	2022-05
Minimum [Member]
Lessee Lease Description [Line Items]
Term of lease contract	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Term of lease contract	15 years

Leases - Schedule of Components

Leases - Schedule of Components of Occupancy Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease Cost [Line Items]
Net lease cost	$ 13,465	$ 11,044
Other, net [Member]
Lease Cost [Line Items]
Operating lease cost for subleased/assigned properties	2,404	2,422
Sublease income for subleased/assigned properties	(2,420)	(2,422)
Occupancy [Member]
Lease Cost [Line Items]
Operating lease cost	13,455	10,875
Variable lease costs	$ 26	$ 169

Leases - Summary of Weighted Av

Leases - Summary of Weighted Average Remaining Lease Term and Discount Rate (Details)	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted average remaining lease term (in years)	12 years 3 months 18 days	13 years 3 months 18 days
Weighted average discount rate	5.90%	5.90%

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
2021	$ 12,131
2022	10,516
2023	10,270
2024	10,937
2025	10,937
2026 and thereafter	79,003
Total lease payments	133,794
Less: interest	40,182
Present value of lease liabilities	$ 93,612	$ 97,991

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Settlement days of bond transaction	within one to two trading days

Segment and Geographic Inform_3

Segment and Geographic Information - Additional Information (Detail) - Segment	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Number of operating segment	1
Geographic Concentration Risk [Member] | Total Revenue and Long-lived Assets [Member] | United Kingdom [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%

Segment and Geographic Inform_4

Segment and Geographic Information - Summary of Revenue and Long-lived Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 689,125	$ 511,352	$ 435,565
Long-lived assets	85,204	71,795
Americas [Member]
Segment Reporting Information [Line Items]
Revenues	583,164	427,276	369,324
Long-lived assets	68,707	62,376
Europe [Member]
Segment Reporting Information [Line Items]
Revenues	89,751	74,511	59,943
Long-lived assets	16,491	9,410
Asia [Member]
Segment Reporting Information [Line Items]
Revenues	16,210	9,565	$ 6,298
Long-lived assets	$ 6	$ 9

Retirement and Deferred Compe_2

Retirement and Deferred Compensation Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Contribution to defined plans	$ 4	$ 3.3	$ 2.6
Non-qualified deferred cash incentive plan maximum eligibility percentage of employees	100.00%
Mutual fund investments and deferred compensation obligation, at fair value	$ 8.9	$ 6.2

Cash and Cash Equivalents and_3

Cash and Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash and Cash Equivalents with Restricted or Segregated Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 460,858	$ 270,124
Cash segregated under federal regulations	50,059
Deposits with clearing organizations and broker-dealers	97,043
Total	608,050	274,253
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	460,858	270,124
Cash Segregated under Federal Regulations and Other [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated under federal regulations	50,059
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Cash And Cash Equivalents [Line Items]
Deposits with clearing organizations and broker-dealers	97,043
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other deposits	$ 90	$ 4,129

Parent Company Information - Co

Parent Company Information - Condensed Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 460,858	$ 270,124
Investments, at fair value	28,111	230,477
Accounts receivable	79,577	62,017
Intangible assets, net of accumulated amortization	95,354	60,986
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	85,204	71,795
Operating lease right-of-use assets	75,924	81,399
Prepaid expenses and other assets	29,039	31,271
Total assets	1,331,429	954,930
Liabilities
Accrued employee compensation	62,326	47,365
Income and other tax liabilities	42,750	16,690
Accounts payable, accrued expenses and other liabilities	44,354	22,793
Operating lease liabilities	93,612	97,991
Total liabilities	376,368	184,839
Stockholders' equity
Preferred stock
Common stock	123	122
Additional paid-in capital	329,742	342,541
Treasury stock	(169,523)	(153,388)
Retained earnings	799,369	591,086
Accumulated other comprehensive loss	(4,650)	(10,270)
Total stockholders' equity	955,061	770,091	$ 607,878	$ 514,768
Total liabilities and stockholders' equity	1,331,429	954,930
MarketAxess Holdings Inc. (Parent) [Member]
ASSETS
Cash and cash equivalents	55,747	48,241
Investments, at fair value	4,811	141,318
Accounts receivable	178	63
Receivable from subsidiaries	41,986	5,997
Intangible assets, net of accumulated amortization	27	30
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	23,518	25,247
Operating lease right-of-use assets	64,460	68,559
Investments in subsidiaries	853,626	570,145
Prepaid expenses and other assets	4,591	6,978
Income and other tax receivable	9,028	3,219
Total assets	1,057,972	869,797
Liabilities
Accrued employee compensation	10,241	6,543
Income and other tax liabilities	3,457
Accounts payable, accrued expenses and other liabilities	9,341	9,254
Operating lease liabilities	79,872	83,909
Total liabilities	102,911	99,706
Stockholders' equity
Preferred stock
Common stock	123	122
Additional paid-in capital	329,742	342,541
Treasury stock	(169,523)	(153,388)
Retained earnings	799,369	591,086
Accumulated other comprehensive loss	(4,650)	(10,270)
Total stockholders' equity	955,061	770,091
Total liabilities and stockholders' equity	1,057,972	869,797
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock
Series A Preferred Stock [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Stockholders' equity
Preferred stock

Parent Company Information - _2

Parent Company Information - Condensed Statements of Operations and Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Expenses
Employee compensation and benefits	$ 156,885	$ 131,079	$ 109,117
Depreciation and amortization	35,996	26,857	23,080
Technology and communications	34,092	26,792	23,866
Professional and consulting fees	32,304	25,534	21,521
Occupancy	13,425	11,639	14,176
General and administrative	12,697	15,696	11,353
Total expenses	314,397	260,470	222,981
Operating (loss) income	374,728	250,882	212,584
Other income (expense)
Investment income	2,446	8,063	6,112
Interest expense	(1,142)
Other, net	(1,673)	(1,521)	(610)
Total other income (expense)	(369)	6,542	5,502
Provision for income taxes	74,982	52,522	45,234
Net income	299,377	204,902	172,852
Comprehensive income	304,997	207,026	170,684
MarketAxess Holdings Inc. (Parent) [Member]
Dividends from subsidiary	30,000	165,000	130,000
Expenses
Employee compensation and benefits	19,710	16,100	10,785
Depreciation and amortization	2,068	1,919	1,760
Technology and communications	10	13	43
Professional and consulting fees	7,332	6,523	4,932
Occupancy	162	850	7,381
General and administrative	2,551	2,252	1,513
Total expenses	31,833	27,657	26,414
Operating (loss) income	(1,833)	137,343	103,586
Other income (expense)
Investment income	2,799	5,305	3,835
Interest expense	(805)
Other, net	(318)	(1,344)	(711)
Total other income (expense)	1,676	3,961	3,124
(Loss) income before income taxes and equity in undistributed earnings of subsidiaries	(157)	141,304	106,710
Provision for income taxes	(23,444)	(9,442)	(7,350)
Income before equity in undistributed income of subsidiaries	23,287	150,746	114,060
Equity in undistributed income of subsidiaries	276,090	54,156	58,792
Net income	299,377	204,902	172,852
Other comprehensive income (loss), net	5,620	2,124	(2,168)
Comprehensive income	$ 304,997	$ 207,026	$ 170,684

Parent Company Information - _3

Parent Company Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income	$ 299,377	$ 204,902	$ 172,852
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35,996	26,857	23,080
Amortization of operating lease right-of-use assets	6,842	5,795
Stock-based compensation expense	25,613	25,294	15,850
Deferred taxes	10,099	2,674	(1,173)
Other	(550)	(778)	2,253
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(18,015)	(2,962)	(5,117)
(Increase) in prepaid expenses and other assets	(1,977)	(4,624)	(3,791)
Decrease (Increase) in trading securities	67,952	4,045	856
Increase in accrued employee compensation	14,961	8,312	2,551
Increase in income and other tax liabilities	16,189	187	2,965
Increase (decrease) in accounts payable, accrued expenses and other liabilities	6,006	(820)	14,524
(Decrease) in operating lease liabilities	(5,788)	(829)
Net cash provided by operating activities	404,489	265,935	223,917
Cash flows from investing activities
Acquisition of business, net of cash and cash equivalents acquired		(97,430)
Proceeds from maturities and sales, available-for-sale investments	170,657	170,936	333,791
Purchases, available-for-sale investments	(32,865)	(160,827)	(336,533)
Purchases of furniture, equipment and leasehold improvements	(15,010)	(12,292)	(35,888)
Capitalization of software development costs	(30,618)	(22,408)	(11,705)
Other		(30)	39
Net cash provided by (used in) investing activities	68,867	(122,051)	(50,296)
Cash flows from financing activities
Cash dividend on common stock	(90,566)	(76,231)	(62,432)
Exercise of stock options	4,007	1,207	2,973
Withholding tax payments on restricted stock vesting and stock option exercises	(42,418)	(25,820)	(8,043)
Repurchases of common stock	(16,135)	(17,256)	(25,171)
Proceeds from short-term borrowings	578,356
Repayments of short-term borrowings	(578,356)
Net cash (used in) financing activities	(145,112)	(118,100)	(92,673)
Effect of exchange rate changes on investments	5,553	1,011	(1,640)
Cash and cash equivalents including restricted cash
Net increase for the period	333,797	26,795	79,308
Beginning of period	274,253	247,458	168,150
End of period	608,050	274,253	247,458
Supplemental cash flow information:
Cash paid for income taxes	45,046	51,766	47,208
Cash paid for interest	1,142
Non-cash investing and financing activity:
Exercise of stock options - cashless	10,866	1,811
Treasury stock used for acquisition of business		(48,830)
MarketAxess Holdings Inc. (Parent) [Member]
Cash flows from operating activities
Net income	299,377	204,902	172,852
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,068	1,919	1,760
Amortization of operating lease right-of-use assets	4,117	4,027
Stock-based compensation expense	10,834	10,547	5,801
Deferred taxes	3,644	1,255	(2,515)
Equity in undistributed income of subsidiaries	(276,090)	(54,156)	(58,792)
Other	(671)	328	710
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(115)	(4)	(14)
(Increase) decrease in receivable from subsidiaries	(25,049)	5,253	15,985
(Increase) in prepaid expenses and other assets	(1,085)	933	(782)
Increase in accrued employee compensation	3,698	876	567
(Increase) in income and other tax receivable	(1,240)	(3,219)
Increase in income and other tax liabilities	6,676	(2,612)	469
Increase (decrease) in accounts payable, accrued expenses and other liabilities	(442)	(2,039)	13,619
(Decrease) in operating lease liabilities	(4,055)	1,191
Net cash provided by operating activities	20,339	168,018	149,190
Cash flows from investing activities
Acquisition of business, net of cash and cash equivalents acquired		(102,320)
Proceeds from maturities and sales, available-for-sale investments	170,657	170,936	333,791
Purchases, available-for-sale investments	(32,865)	(160,827)	(336,533)
Purchases of furniture, equipment and leasehold improvements	(337)	(1,424)	(24,786)
Purchase of intangible asset		(30)
Net cash provided by (used in) investing activities	137,455	(93,665)	(27,528)
Cash flows from financing activities
Cash dividend on common stock	(90,566)	(76,231)	(62,432)
Exercise of stock options	4,007	1,207	2,973
Withholding tax payments on restricted stock vesting and stock option exercises	(42,418)	(25,820)	(8,043)
Repurchases of common stock	(16,135)	(17,256)	(25,171)
Proceeds from short-term borrowings	348,000
Repayments of short-term borrowings	(348,000)
Net cash (used in) financing activities	(145,112)	(118,100)	(92,673)
Effect of exchange rate changes on investments	(5,176)	(3,852)	4,129
Cash and cash equivalents including restricted cash
Net increase for the period	7,506	(47,599)	33,118
Beginning of period	48,241	95,840	62,722
End of period	55,747	48,241	95,840
Supplemental cash flow information:
Cash paid for income taxes	32,674	41,025	37,721
Cash paid for interest	805
Non-cash investing and financing activity:
Exercise of stock options - cashless	10,866	1,811
Treasury stock used for acquisition of business		(48,830)
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease (Increase) in trading securities	(2,671)	(2,118)	(933)
Mutual Funds Held In Rabbi Trust [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Changes in operating assets and liabilities:
Decrease (Increase) in trading securities	$ (1,328)	$ (1,183)	$ (470)