MarketAxess (MKTX) 10-Q 28 Apr 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 23, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Trading Symbol	MKTX
Entity Registrant Name	MARKETAXESS HOLDINGS INC.
Entity Central Index Key	0001278021
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		37,982,694
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
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, Address Line Two	15th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10001
Document Quarterly Report	true
Document Transition Report	false
City Area Code	212
Local Phone Number	813-6000

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ASSETS
Cash and cash equivalents	$ 390,915	$ 460,858
Cash segregated under federal regulations	50,083	50,059
Investments, at fair value	24,308	28,111
Accounts receivable, net of allowance of $107 and $163 as of March 31, 2021 and December 31, 2020, respectively	87,452	79,577
Receivables from broker-dealers, clearing organizations and customers	564,957	279,915
Goodwill	147,388	147,388
Intangible assets, net of accumulated amortization	90,945	95,354
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	88,655	85,204
Operating lease right-of-use assets	75,223	75,924
Prepaid expenses and other assets	25,943	29,039
Total assets	1,545,869	1,331,429
Liabilities
Accrued employee compensation	28,223	62,326
Payables to broker-dealers, clearing organizations and customers	308,268	133,326
Income and other tax liabilities	48,193	42,750
Accounts payable, accrued expenses and other liabilities	80,202	44,354
Operating lease liabilities	92,750	93,612
Total liabilities	557,636	376,368
Commitments and Contingencies (Note 13)
Stockholders' equity
Preferred stock
Common stock	123	123
Additional paid-in capital	309,988	329,742
Treasury stock - Common stock voting, at cost, 2,844,954 and 2,845,770 shares as of March 31, 2021 and December 31, 2020, respectively	(170,043)	(169,523)
Retained earnings	854,747	799,369
Accumulated other comprehensive loss	(6,582)	(4,650)
Total stockholders' equity	988,233	955,061
Total liabilities and stockholders' equity	1,545,869	1,331,429
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Allowance for accounts receivable	$ 107	$ 163
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	40,830,772	40,851,100
Common stock, shares outstanding	37,985,818	38,005,330
Treasury stock, shares	2,844,954	2,845,770
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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues
Revenues	$ 195,464	$ 168,978
Expenses
Employee compensation and benefits	48,088	41,194
Depreciation and amortization	11,779	8,067
Technology and communications	10,036	8,161
Professional and consulting fees	9,640	5,675
Occupancy	3,317	3,474
Marketing and advertising	1,204	2,675
Clearing costs	4,694	5,510
General and administrative	3,232	3,133
Total expenses	91,990	77,889
Operating income	103,474	91,089
Other income (expense)
Investment income	107	1,269
Interest expense	(191)
Other, net	(1,589)	(656)
Total other income (expense)	(1,673)	613
Income before income taxes	101,801	91,702
Provision for income taxes	21,344	16,886
Net income	$ 80,457	$ 74,816
Net income per common share
Basic	$ 2.15	$ 2.01
Diluted	2.11	1.96
Cash dividends declared per common share	$ 0.66	$ 0.60
Weighted average shares outstanding
Basic	37,470	37,303
Diluted	38,155	38,075
Commissions [Member]
Revenues
Revenues	$ 175,838	$ 155,954
Information Services [Member]
Revenues
Revenues	9,162	8,642
Post-trade Services [Member]
Revenues
Revenues	10,261	4,153
Other [Member]
Revenues
Revenues	$ 203	$ 229

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 80,457	$ 74,816
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(413) and $2,441, respectively	(1,932)	(3,859)
Net unrealized (loss) on securities available-for-sale, net of tax of $(155)		(491)
Comprehensive income	$ 78,525	$ 70,466

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency exchange hedge, tax expense (benefit)	$ (413)	$ 2,441
Securities available-for-sale, tax expense (benefit)	$ (155)	$ (155)

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, 2019	$ 770,091	$ 122	$ 342,541	$ (153,388)	$ 591,086	$ (10,270)
Net income	74,816				74,816
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(3,859)					(3,859)
Unrealized net loss on securities available-for-sale, net of tax	(491)					(491)
Stock-based compensation	6,677		6,677
Exercise of stock options	80		80
Withholding tax payments on restricted stock vesting and stock option exercises	(21,243)		(21,243)
Repurchases of common stock	(5,415)			(5,415)
Cash dividend on common stock	(22,773)				(22,773)
Ending Balance at Mar. 31, 2020	797,883	122	328,055	(158,803)	643,129	(14,620)
Beginning Balance at Dec. 31, 2020	955,061	123	329,742	(169,523)	799,369	(4,650)
Net income	80,457				80,457
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(1,932)					(1,932)
Stock-based compensation	7,424		7,424
Exercise of stock options	244		244
Withholding tax payments on restricted stock vesting and stock option exercises	(27,422)		(27,422)
Repurchases of common stock	(520)			(520)
Cash dividend on common stock	(25,079)				(25,079)
Ending Balance at Mar. 31, 2021	$ 988,233	$ 123	$ 309,988	$ (170,043)	$ 854,747	$ (6,582)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Stockholders Equity [Abstract]
Cash dividends declared per common share	$ 0.66	$ 0.60

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 80,457	$ 74,816
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	11,779	8,067
Amortization of operating lease right-of-use assets	1,664	1,645
Stock-based compensation expense	7,424	6,677
Deferred taxes	591	2,734
Other	(74)	2,036
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(7,880)	(31,640)
(Increase) in receivables from broker-dealers, clearing organizations and customers	(270,491)
Decrease in prepaid expenses and other assets	3,082	8,539
Decrease in trading investments	5,495	56,394
(Decrease) in accrued employee compensation	(34,103)	(25,436)
Increase in payables to broker-dealers, clearing organizations and customers	174,942
Increase in income and other tax liabilities	4,814	1,950
Increase in accounts payable, accrued expenses and other liabilities	2,599	16,392
(Decrease) in operating lease liabilities	(1,845)	(1,516)
Net cash (used in) provided by operating activities	(23,159)	120,369
Cash flows from investing activities
Acquisition of business		(533)
Proceeds from maturities and sales, available-for-sale investments		45,154
Purchases, available-for-sale investments		(8,995)
Purchases of furniture, equipment and leasehold improvements	(4,257)	(4,291)
Capitalization of software development costs	(8,075)	(6,778)
Net cash (used in) provided by investing activities	(12,332)	24,557
Cash flows from financing activities
Cash dividend on common stock	(25,454)	(23,244)
Exercise of stock options	244	80
Withholding tax payments on restricted stock vesting and stock option exercises	(27,422)	(21,243)
Repurchases of common stock	(520)	(5,415)
Proceeds from short-term borrowings	69,302
Repayments of short-term borrowings	(35,000)
Net cash (used in) financing activities	(18,850)	(49,822)
Effect of exchange rate changes on cash and cash equivalents	(1,027)	(3,360)
Cash and cash equivalents including restricted cash
Net (decrease) increase for the period	(55,368)	91,744
Beginning of period	608,050	274,253
End of period	552,682	365,997
Non-cash activity
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	878	674
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease in trading investments	$ (1,613)	$ (289)

Organization and Principal Busi

Organization and Principal Business Activity	3 Months Ended
	Mar. 31, 2021
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. ®

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
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. These consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The consolidated financial information as of December 31, 2020 has been derived from audited financial statements not included herein. These unaudited consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) with respect to Form 10-Q and reflect all adjustments that, in the opinion of management, are normal and recurring, and that are necessary for a fair statement of the results for the interim periods presented. In accordance with such rules and regulations, certain disclosures that are normally included in annual financial statements have been omitted. Interim period operating results may not be indicative of the operating results for a full year. 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, Not Yet Adopted In March 2020, the Financial Accounting Standards Board (“FASB”) issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (the “ASU”), which is designed to ease the potential burden in accounting for the transition away from the London Inter-bank Offered Rate (“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 Financial Statements. 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. 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 carried at fair value, with realized and unrealized gains or losses included in other, net in the Consolidated Statements of Operations. 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 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. 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 Consolidated Statement of Financial Condition 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, are 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, as well as 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: Three Months Ended March 31, 2021 2020 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 98,818 $ 84,245 Open Trading - matched principal trading 46,320 40,358 U.S. Treasuries - matched principal trading 3,260 4,563 Total variable transaction fees 148,398 129,166 Distribution fees and unused minimum fees 27,440 26,788 Total commissions $ 175,838 $ 155,954 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: Three Months Ended March 31, 2021 2020 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 9,045 $ 7,806 Services transferred at a point in time 117 836 Total information services revenues $ 9,162 $ 8,642 Post-trade services – Post-trade services revenue is generated from regulatory transaction reporting, trade publication and trade matching services. Customers are generally billed in the current month or 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: Three Months Ended March 31, 2021 2020 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 10,020 $ 4,150 Services transferred at a point in time 241 3 Total post-trade services revenues $ 10,261 $ 4,153 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, 2020 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation March 31, 2021 (In thousands) Information services $ 3,203 $ 2,417 $ (2,454 ) $ — $ 3,166 Post-trade services 1,045 4,607 (4,003 ) 10 1,659 Total deferred revenue $ 4,248 $ 7,024 $ (6,457 ) $ 10 $ 4,825 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 $21.6 million as of March 31, 2021. The Company expects to recognize revenue associated with the remaining performance obligations over the next 30 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 requires judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth 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 GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Regulatory Capital Requirements

Regulatory Capital Requirements	3 Months Ended
	Mar. 31, 2021
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 (“SEF”) and therefore are subject to the applicable rules and regulations of the SEC and the Commodity Futures Trading Commission (“CFTC”). These rules contain minimum net capital requirements, as defined in the applicable regulations, and also may require that 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 (“FCA”) 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 March 31, 2021, 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 March 31, 2021, the Company’s subsidiaries maintained aggregate net capital and financial resources that were $493.5 million in excess of the required levels of $31.1 million. One of the Company’s U.S. broker-dealer subsidiaries 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 March 31, 2021, 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	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 Money market funds $ 11,327 $ — $ — $ 11,327 Trading securities Corporate debt — 13,806 — 13,806 Mutual funds held in rabbi trust — 10,502 — 10,502 Foreign currency forward position — (1,349 ) — (1,349 ) Total $ 11,327 $ 22,959 $ — $ 34,286 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 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 three months ended March 31, 2021 and 2020. 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 March 31, 2021 Financial assets not measured at fair value: Cash and cash equivalents $ 390,915 $ 390,915 $ 390,915 $ — $ — $ 390,915 Cash segregated under federal regulations 50,083 50,083 50,083 — — 50,083 Accounts receivable, net of allowance 87,452 87,452 87,452 — — 87,452 Receivables from broker-dealers, clearing organizations and customers 564,957 564,957 111,594 453,363 — 564,957 Total $ 1,093,407 $ 1,093,407 $ 640,044 $ 453,363 $ — $ 1,093,407 Financial liabilities not measured at fair value: Payables to broker-dealers, clearing organizations and customers $ 308,268 $ 308,268 $ — $ 308,268 $ — $ 308,268 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 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 March 31, 2021 December 31, 2020 (In thousands) Notional value $ 196,085 $ 157,057 Fair value of notional 197,434 157,862 Fair value of the (liability) $ (1,349 ) $ (805 ) The following table summarizes the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Fair value (In thousands) As of March 31, 2021 Trading securities Corporate debt $ 13,721 $ 85 $ — $ 13,806 Mutual funds held in rabbi trust 10,172 330 — 10,502 Total trading securities 23,893 415 — 24,308 Total investments $ 23,893 $ 415 $ — $ 24,308 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 The following table summarizes the fair value of the investments based upon the contractual maturities: As of March 31, 2021 December 31, 2020 (In thousands) Less than one year $ 17,191 $ 18,290 Due in 1 - 5 years 7,117 9,821 Total $ 24,308 $ 28,111 Proceeds from the sales and maturities of investments during the three months ended March 31, 2021 and 2020 were $5.5 million and $111.4 million, respectively.

Receivables from and Payables t

Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers	3 Months Ended
	Mar. 31, 2021
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 Receivables from and payables to broker-dealers, clearing organizations and customers consisted of the following: March 31, 2021 December 31, 2020 Receivables from broker-dealers, clearing organizations and customers: (In thousands) Securities failed-to-deliver - broker-dealers $ 155,693 $ 93,294 Securities failed-to-deliver - customers 288,235 87,685 Deposits with clearing organizations and broker-dealers 111,594 97,043 Other 9,435 1,893 Total $ 564,957 $ 279,915 Payables to broker-dealers, clearing organizations and customers: Securities failed-to-receive - broker-dealers 156,322 70,917 Securities failed-to-receive - customers 144,958 60,784 Other 6,988 1,625 Total $ 308,268 $ 133,326

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Acquisitions	6. Acquisitions On November 30, 2020, the Company acquired Regulatory Services GmbH, the pan-European regulatory reporting business of Deutsche B örse Group. The purchase price consists of $22.5 million in cash paid at closing and up to $24.6 million in contingent consideration payable in cash within 18 months of the closing. The Company is accounting for the transaction as a purchase of assets and recorded $37.4 million in amortizable intangible assets as of the acquisition date. On April 9, 2021, the Company acquired MuniBrokers LLC, a central electronic venue serving municipal bond brokers and dealers. The purchase price consists of $17.0 million in cash paid at closing and up to $25.0 million in contingent consideration payable within approximately two years of the closing.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2021
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 million as of March 31, 2021 and December 31, 2020. Intangible assets that are subject to amortization, including the related accumulated amortization, are comprised of the following: March 31, 2021 December 31, 2020 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Customer relationships $ 100,962 $ (10,044 ) $ 90,918 $ 102,696 $ (7,369 ) $ 95,327 Technology and other intangibles 6,550 (6,523 ) 27 6,550 (6,523 ) 27 Total $ 107,512 $ (16,567 ) $ 90,945 $ 109,246 $ (13,892 ) $ 95,354 Amortization expense associated with identifiable intangible assets was $2.7 million and $0.7 million for the three months ended March 31, 2021 and 2020, respectively. Estimated total amortization expense associated with the Company’s intangible assets as of March 31, 2021 is $5.7 million, $6.9 million, $7.9 million, $6.7 million and $5.7 million, respectively, for each year from 2021 through 2025.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The provision for income taxes consists of the following: Three Months Ended March 31, 2021 2020 Current: (In thousands) Federal $ 12,523 $ 7,766 State and local 3,411 2,910 Foreign 4,819 3,447 Total current provision 20,753 14,123 Deferred: Federal 602 1,905 State and local 101 352 Foreign (112 ) 506 Total deferred provision 591 2,763 Provision for income taxes $ 21,344 $ 16,886 Effective tax rate 21.0 % 18.4 % T he Company recognized excess tax benefits on share-based payments of $ million and $ million through the provision for income taxes for the three months ended March 31, 2021 and 2020, respectively. 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 the 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.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Plans	9. Stock-Based Compensation Plans Total stock-based compensation expense was as follows: Three Months Ended March 31, 2021 2020 (In thousands) Employees $ 7,103 $ 6,399 Non-employee directors 321 278 Total stock-based compensation $ 7,424 $ 6,677 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. During the three months ended March 31, 2021, the Company granted to employees a total of 32,251 shares of restricted stock or restricted stock units, 15,982 options to purchase shares of common stock and performance-based shares with an expected pay-out at target of 12,185 shares of common stock. The fair value of the restricted stock and performance-based share awards was based on a weighted-average fair value per share at the grant date of $526.50 and $523.00, respectively. Based on the Black-Scholes option pricing model, the weighted-average fair value for each option granted was $138.51 per share. As of March 31, 2021, the total unrecognized compensation cost related to all non-vested awards was $50.9 million. That cost is expected to be recognized over a weighted-average period of 2.2 years.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Share	10. Earnings Per Share The following table sets forth basic and diluted weighted average shares outstanding used to compute earnings per share: Three Months Ended March 31, 2021 2020 (In thousands, except per share amounts) Basic weighted average shares outstanding 37,470 37,303 Dilutive effect of stock options and restricted stock 685 772 Diluted weighted average shares outstanding 38,155 38,075 Basic earnings per share $ 2.15 $ 2.01 Diluted earnings per share 2.11 1.96 Stock options and restricted stock totaling 61,089 shares and 62,964 shares for the three months ended March 31, 2021 and 2020, 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 Agreements and Short-ter

Credit Agreements and Short-term Financing	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Credit Agreements and Short-term Financing	11. Credit Agreements and Short-term Financing Prior Revolving Credit Agreement In October 2015, the Company entered into an amended and restated credit agreement (the “Prior Credit Agreement”) that provided for revolving loans and letters of credit up to an aggregate of $100.0 million. The Prior Credit Agreement matured on November 13, 2020, when the Company entered into a new one-year Revolving Credit Agreement On November 13, 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 $500.0 million, consisting of a revolving credit facility and a $5.0 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 $250.0 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 March 31, 2021. The Company incurred no interest expense under the Credit Agreement for the three months ended March 31, 2021. Collateralized Agreement In connection with its self-clearing operations, one of the Company’s U.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 less than $0.1 million of interest expense on borrowings under the Collateralized Agreement during the three months ended March 31, 2021. As of March 31, 2021, the Company had no borrowings outstanding and $200.0 million in available borrowing capacity under the Collateralized Agreement. Short-term Financing Under an arrangement with its settlement bank, one of the Company’s U.K. subsidiaries received overnight financing in the form of bank overdrafts. The U.K. subsidiary incurred interest expense on such overnight financing of $0.2 million during the three months ended March 31, 2021. As of March 31, 2021, the U.K. subsidiary had $34.3 million of overdrafts payable outstanding which is included within accounts payable, accrued expenses and other liabilities on the Consolidated Statement of Financial Condition.

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	12. Leases The Company has operating leases for corporate offices with initial lease terms ranging from one year to 15 years. Certain leases contain options to extend the initial term at the Company’s discretion. The Company accounts for the option to extend when it is reasonably certain of being exercised. The Company’s lease agreements do not contain any material residual value guarantees, restrictions or covenants. The following table presents the components of lease expense: Three Months Ended March 31, Lease cost: Classification 2021 2020 (In thousands) Operating lease cost Occupancy $ 3,323 $ 3,449 Operating lease cost for subleased/assigned properties Other, net 497 536 Variable lease costs Occupancy 6 16 Sublease income subleased/assigned properties Other, net (502 ) (536 ) Net lease cost $ 3,324 $ 3,465 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 (in years) and weighted average discount rate are as follows: As of Lease Term and Discount Rate March 31, 2021 December 31, 2020 Weighted average remaining lease term (in years) 12.0 12.3 Weighted average discount rate 5.9 % 5.9 % The following table presents the maturity of lease liabilities as of March 31, 2021: (In thousands) Remainder of 2021 $ 9,177 2022 10,692 2023 10,451 2024 11,122 2025 11,127 2026 and thereafter 79,095 Total lease payments 131,664 Less: interest 38,914 Operating lease liabilities $ 92,750 The Company has entered into agreements that 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 $1.7 million as of March 31, 2021.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. 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 will establish an accrual for the loss. Once established, the accrual will 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 In the normal course of business, the Company enters into contracts that contain a variety of representations, warranties and indemnification provisions. 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.

Share Repurchase Program

Share Repurchase Program	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Share Repurchase Program	14. Share Repurchase Program In January 2019, the Board of Directors authorized a two-year

Segment and Geographic Informat

Segment and Geographic Information	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment and Geographic Information	15. Segment and Geographic Information The Company operates an electronic platform for the trading of fixed-income securities and provides related data, analytics, compliance tools and post-trade services. The Company considers its operations to constitute a single For the three months ended March 31, 2021 and 2020, 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 of the Company. Revenues and long-lived assets are attributed to a 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 months ended March 31, 2021 and 2020 and long-lived assets as of March 31, 2021 and December 31, 2020 were as follows: Three Months Ended March 31, 2021 2020 (In thousands) Revenues Americas $ 160,119 $ 142,637 Europe 29,544 22,419 Asia 5,801 3,922 Total $ 195,464 $ 168,978 As of March 31, 2021 December 31, 2020 (In thousands) Long-lived assets, as defined Americas $ 70,812 $ 68,707 Europe 17,838 16,491 Asia 5 6 Total $ 88,655 $ 85,204

Cash and Cash Equivalents and R

Cash and Cash Equivalents and Restricted Cash	3 Months Ended
	Mar. 31, 2021
Cash And Cash Equivalents [Abstract]
Cash and Cash Equivalents and Restricted Cash	16. 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 March 31, 2021 December 31, 2020 (In thousands) Cash and cash equivalents Cash and cash equivalents $ 390,915 $ 460,858 Cash segregated for regulatory purposes Cash segregated under federal regulations 50,083 50,059 Deposits with clearing organizations and broker-dealers Receivables from broker-dealers, clearing organizations and customers 111,594 97,043 Other deposits Prepaid expenses and other assets 90 90 Total $ 552,682 $ 608,050

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
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. These consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. The consolidated financial information as of December 31, 2020 has been derived from audited financial statements not included herein. These unaudited consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) with respect to Form 10-Q and reflect all adjustments that, in the opinion of management, are normal and recurring, and that are necessary for a fair statement of the results for the interim periods presented. In accordance with such rules and regulations, certain disclosures that are normally included in annual financial statements have been omitted. Interim period operating results may not be indicative of the operating results for a full year. 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 Not Yet Adopted	Accounting Pronouncements, Not Yet Adopted In March 2020, the Financial Accounting Standards Board (“FASB”) issued ASU 2020-04, “Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (the “ASU”), which is designed to ease the potential burden in accounting for the transition away from the London Inter-bank Offered Rate (“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 Financial Statements.
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. 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 carried at fair value, with realized and unrealized gains or losses included in other, net in the Consolidated Statements of Operations.
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 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.
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 Consolidated Statement of Financial Condition 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, are 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, as well as 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: Three Months Ended March 31, 2021 2020 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 98,818 $ 84,245 Open Trading - matched principal trading 46,320 40,358 U.S. Treasuries - matched principal trading 3,260 4,563 Total variable transaction fees 148,398 129,166 Distribution fees and unused minimum fees 27,440 26,788 Total commissions $ 175,838 $ 155,954 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: Three Months Ended March 31, 2021 2020 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 9,045 $ 7,806 Services transferred at a point in time 117 836 Total information services revenues $ 9,162 $ 8,642 Post-trade services – Post-trade services revenue is generated from regulatory transaction reporting, trade publication and trade matching services. Customers are generally billed in the current month or 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: Three Months Ended March 31, 2021 2020 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 10,020 $ 4,150 Services transferred at a point in time 241 3 Total post-trade services revenues $ 10,261 $ 4,153 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, 2020 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation March 31, 2021 (In thousands) Information services $ 3,203 $ 2,417 $ (2,454 ) $ — $ 3,166 Post-trade services 1,045 4,607 (4,003 ) 10 1,659 Total deferred revenue $ 4,248 $ 7,024 $ (6,457 ) $ 10 $ 4,825 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 $21.6 million as of March 31, 2021. The Company expects to recognize revenue associated with the remaining performance obligations over the next 30 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 requires judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth 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 GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Commission Revenue by Fee Type	The following table presents commission revenue by fee type: Three Months Ended March 31, 2021 2020 (In thousands) Commission revenue by fee type Variable transaction fees Disclosed trading $ 98,818 $ 84,245 Open Trading - matched principal trading 46,320 40,358 U.S. Treasuries - matched principal trading 3,260 4,563 Total variable transaction fees 148,398 129,166 Distribution fees and unused minimum fees 27,440 26,788 Total commissions $ 175,838 $ 155,954
Summary of Information Services Revenue by Timing of Recognition	The following table presents information services revenue by timing of recognition: Three Months Ended March 31, 2021 2020 (In thousands) Information services revenue by timing of recognition Services transferred over time $ 9,045 $ 7,806 Services transferred at a point in time 117 836 Total information services revenues $ 9,162 $ 8,642
Summary of Post-Trade Services Revenue by Timing of Recognition	The following table presents post-trade services revenue by timing of recognition: Three Months Ended March 31, 2021 2020 (In thousands) Post-trade services revenue by timing of recognition Services transferred over time $ 10,020 $ 4,150 Services transferred at a point in time 241 3 Total post-trade services revenues $ 10,261 $ 4,153
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, 2020 Payments received in advance of services to be performed Revenue recognized for services performed during the period Foreign Currency Translation March 31, 2021 (In thousands) Information services $ 3,203 $ 2,417 $ (2,454 ) $ — $ 3,166 Post-trade services 1,045 4,607 (4,003 ) 10 1,659 Total deferred revenue $ 4,248 $ 7,024 $ (6,457 ) $ 10 $ 4,825

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 Money market funds $ 11,327 $ — $ — $ 11,327 Trading securities Corporate debt — 13,806 — 13,806 Mutual funds held in rabbi trust — 10,502 — 10,502 Foreign currency forward position — (1,349 ) — (1,349 ) Total $ 11,327 $ 22,959 $ — $ 34,286 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
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 March 31, 2021 Financial assets not measured at fair value: Cash and cash equivalents $ 390,915 $ 390,915 $ 390,915 $ — $ — $ 390,915 Cash segregated under federal regulations 50,083 50,083 50,083 — — 50,083 Accounts receivable, net of allowance 87,452 87,452 87,452 — — 87,452 Receivables from broker-dealers, clearing organizations and customers 564,957 564,957 111,594 453,363 — 564,957 Total $ 1,093,407 $ 1,093,407 $ 640,044 $ 453,363 $ — $ 1,093,407 Financial liabilities not measured at fair value: Payables to broker-dealers, clearing organizations and customers $ 308,268 $ 308,268 $ — $ 308,268 $ — $ 308,268 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
Summary of Foreign Currency Forward Contracts	The following table summarizes the Company’s foreign currency forward position: As of March 31, 2021 December 31, 2020 (In thousands) Notional value $ 196,085 $ 157,057 Fair value of notional 197,434 157,862 Fair value of the (liability) $ (1,349 ) $ (805 )
Summary of Company's Investments	The following table summarizes the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Fair value (In thousands) As of March 31, 2021 Trading securities Corporate debt $ 13,721 $ 85 $ — $ 13,806 Mutual funds held in rabbi trust 10,172 330 — 10,502 Total trading securities 23,893 415 — 24,308 Total investments $ 23,893 $ 415 $ — $ 24,308 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
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 March 31, 2021 December 31, 2020 (In thousands) Less than one year $ 17,191 $ 18,290 Due in 1 - 5 years 7,117 9,821 Total $ 24,308 $ 28,111

Receivables from and Payables_2

Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers (Tables)	3 Months Ended
	Mar. 31, 2021
Due To And From Broker Dealers And Clearing Organizations [Abstract]
Schedule of Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers	Receivables from and payables to broker-dealers, clearing organizations and customers consisted of the following: March 31, 2021 December 31, 2020 Receivables from broker-dealers, clearing organizations and customers: (In thousands) Securities failed-to-deliver - broker-dealers $ 155,693 $ 93,294 Securities failed-to-deliver - customers 288,235 87,685 Deposits with clearing organizations and broker-dealers 111,594 97,043 Other 9,435 1,893 Total $ 564,957 $ 279,915 Payables to broker-dealers, clearing organizations and customers: Securities failed-to-receive - broker-dealers 156,322 70,917 Securities failed-to-receive - customers 144,958 60,784 Other 6,988 1,625 Total $ 308,268 $ 133,326

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2021
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: March 31, 2021 December 31, 2020 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Customer relationships $ 100,962 $ (10,044 ) $ 90,918 $ 102,696 $ (7,369 ) $ 95,327 Technology and other intangibles 6,550 (6,523 ) 27 6,550 (6,523 ) 27 Total $ 107,512 $ (16,567 ) $ 90,945 $ 109,246 $ (13,892 ) $ 95,354

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Provision for Income Taxes	The provision for income taxes consists of the following: Three Months Ended March 31, 2021 2020 Current: (In thousands) Federal $ 12,523 $ 7,766 State and local 3,411 2,910 Foreign 4,819 3,447 Total current provision 20,753 14,123 Deferred: Federal 602 1,905 State and local 101 352 Foreign (112 ) 506 Total deferred provision 591 2,763 Provision for income taxes $ 21,344 $ 16,886 Effective tax rate 21.0 % 18.4 %

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense	Total stock-based compensation expense was as follows: Three Months Ended March 31, 2021 2020 (In thousands) Employees $ 7,103 $ 6,399 Non-employee directors 321 278 Total stock-based compensation $ 7,424 $ 6,677

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
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: Three Months Ended March 31, 2021 2020 (In thousands, except per share amounts) Basic weighted average shares outstanding 37,470 37,303 Dilutive effect of stock options and restricted stock 685 772 Diluted weighted average shares outstanding 38,155 38,075 Basic earnings per share $ 2.15 $ 2.01 Diluted earnings per share 2.11 1.96

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Schedule of Components of Lease Expense	The following table presents the components of lease expense: Three Months Ended March 31, Lease cost: Classification 2021 2020 (In thousands) Operating lease cost Occupancy $ 3,323 $ 3,449 Operating lease cost for subleased/assigned properties Other, net 497 536 Variable lease costs Occupancy 6 16 Sublease income subleased/assigned properties Other, net (502 ) (536 ) Net lease cost $ 3,324 $ 3,465
Summary of Weighted Average Remaining Lease Term and Discount Rate	The weighted average remaining lease term (in years) and weighted average discount rate are as follows: As of Lease Term and Discount Rate March 31, 2021 December 31, 2020 Weighted average remaining lease term (in years) 12.0 12.3 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 March 31, 2021: (In thousands) Remainder of 2021 $ 9,177 2022 10,692 2023 10,451 2024 11,122 2025 11,127 2026 and thereafter 79,095 Total lease payments 131,664 Less: interest 38,914 Operating lease liabilities $ 92,750

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Summary of Revenue and Long-lived Assets	Revenues for the three months ended March 31, 2021 and 2020 and long-lived assets as of March 31, 2021 and December 31, 2020 were as follows: Three Months Ended March 31, 2021 2020 (In thousands) Revenues Americas $ 160,119 $ 142,637 Europe 29,544 22,419 Asia 5,801 3,922 Total $ 195,464 $ 168,978 As of March 31, 2021 December 31, 2020 (In thousands) Long-lived assets, as defined Americas $ 70,812 $ 68,707 Europe 17,838 16,491 Asia 5 6 Total $ 88,655 $ 85,204

Cash and Cash Equivalents and_2

Cash and Cash Equivalents and Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2021
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 March 31, 2021 December 31, 2020 (In thousands) Cash and cash equivalents Cash and cash equivalents $ 390,915 $ 460,858 Cash segregated for regulatory purposes Cash segregated under federal regulations 50,083 50,059 Deposits with clearing organizations and broker-dealers Receivables from broker-dealers, clearing organizations and customers 111,594 97,043 Other deposits Prepaid expenses and other assets 90 90 Total $ 552,682 $ 608,050

Organization and Principal Bu_2

Organization and Principal Business Activity - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021Institutional_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)	3 Months Ended
	Mar. 31, 2021Revenue
Significant Accounting Policies [Line Items]
Maximum maturity period for classification of investments as cash equivalents	3 months
Number of revenue streams	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

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Commission Revenue by Fee Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commission revenue by fee type
Revenues	$ 195,464	$ 168,978
Commissions [Member]
Commission revenue by fee type
Disclosed trading	98,818	84,245
Matched principal trading	46,320	40,358
Total variable transaction fees	148,398	129,166
Distribution fees and unused minimum fees	27,440	26,788
Revenues	175,838	155,954
Commissions [Member] | U.S. Treasuries [Member]
Commission revenue by fee type
Matched principal trading	$ 3,260	$ 4,563

Significant Accounting Polici_6

Significant Accounting Policies - Summary of Information Services Revenue by Timing of Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Significant Accounting Policies [Line Items]
Revenues	$ 195,464	$ 168,978
Information Services [Member]
Significant Accounting Policies [Line Items]
Revenues	9,162	8,642
Information Services [Member] | Transferred over Time [Member]
Significant Accounting Policies [Line Items]
Revenues	9,045	7,806
Information Services [Member] | Transferred at a Point in Time [Member]
Significant Accounting Policies [Line Items]
Revenues	$ 117	$ 836

Significant Accounting Polici_7

Significant Accounting Policies - Summary of Post-Trade Services Revenue by Timing of Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Significant Accounting Policies [Line Items]
Revenues	$ 195,464	$ 168,978
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Revenues	10,261	4,153
Post-trade Services [Member] | Transferred over Time [Member]
Significant Accounting Policies [Line Items]
Revenues	10,020	4,150
Post-trade Services [Member] | Transferred at a Point in Time [Member]
Significant Accounting Policies [Line Items]
Revenues	$ 241	$ 3

Significant Accounting Polici_8

Significant Accounting Policies - Summary of Revenue Recognized from Contract Liabilities and Remaining Balance (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	$ 4,248
Payments received in advance of services to be performed	7,024
Revenue recognized for services performed during the period	(6,457)
Foreign Currency Translation	10
Deferred revenues, ending balance	4,825
Information Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	3,203
Payments received in advance of services to be performed	2,417
Revenue recognized for services performed during the period	(2,454)
Deferred revenues, ending balance	3,166
Post-trade Services [Member]
Significant Accounting Policies [Line Items]
Deferred revenues, beginning balance	1,045
Payments received in advance of services to be performed	4,607
Revenue recognized for services performed during the period	(4,003)
Foreign Currency Translation	10
Deferred revenues, ending balance	$ 1,659

Significant Accounting Polici_9

Significant Accounting Policies - Additional Information (Detail 1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-04-01 $ in Millions	Mar. 31, 2021USD ($)
Significant Accounting Policies [Line Items]
Aggregate amount of transaction price allocated to remaining performance obligations	$ 21.6
Expected time to recognize revenue for remaining performance obligation	30 months

Regulatory Capital Requiremen_2

Regulatory Capital Requirements - Additional Information (Detail) $ in Millions	Mar. 31, 2021USD ($)
Brokers And Dealers [Abstract]
Aggregate net capital and financial resources in excess of required level	$ 493.5
Aggregate net capital and financial resources, minimum capital requirement	31.1
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	Mar. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	$ 11,327	$ 20,856
Trading securities	24,308
Assets Fair Value Total	34,286	48,162
Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	13,806	19,222
Mutual Funds Held In Rabbi Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	10,502	8,889
Foreign Currency Forward Position [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	(1,349)	(805)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	11,327	20,856
Assets Fair Value Total	11,327	20,856
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Fair Value Total	22,959	27,306
Level 2 [Member] | Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	13,806	19,222
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	10,502	8,889
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	$ (1,349)	$ (805)

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Value of Financial Asset and Liability Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financial assets not measured at fair value:
Financial assets not measured at fair value	$ 34,286	$ 48,162
Level 1 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	11,327	20,856
Level 2 [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	22,959	27,306
Financial Assets and Liabilities not Measured [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	1,093,407	870,409
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	308,268	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	390,915	460,858
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	50,083	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	87,452	79,577
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	564,957	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	640,044	607,960
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	390,915	460,858
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	50,083	50,059
Financial Assets and Liabilities not Measured [Member] | Level 1 [Member] | Accounts Receivable, Net of Allowance [Member]
Financial assets not measured at fair value:
Financial assets not measured at fair value	87,452
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	111,594	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	453,363	262,449
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	308,268	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
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	453,363	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	1,093,407	870,409
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	308,268	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	390,915	460,858
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	50,083	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	87,452	79,577
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	564,957	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	1,093,407	870,409
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	308,268	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	390,915	460,858
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	50,083	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	87,452	79,577
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	$ 564,957	$ 279,915

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Hedge derivative expiration period	1 month
Proceeds from the sales and maturities of securities available-for-sale	$ 5.5	$ 111.4

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Foreign Currency Forward Contracts (Detail) - Foreign Currency Forward Position [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Derivatives Fair Value [Line Items]
Notional value	$ 196,085	$ 157,057
Fair value of notional	197,434	157,862
Fair value of the (liability)	$ (1,349)	$ (805)

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Company's Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	$ 23,893
Trading securities, Gross unrealized gains	415
Trading securities, Fair value	24,308
Investments, Amortized cost	23,893	$ 26,761
Investments, Gross unrealized gains	415	1,350
Investments, Fair value	24,308	28,111
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	13,721	19,081
Trading securities, Gross unrealized gains	85	141
Trading securities, Fair value	13,806	19,222
Mutual Funds Held In Rabbi Trust [Member]
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	10,172	7,680
Trading securities, Gross unrealized gains	330	1,209
Trading securities, Fair value	$ 10,502	$ 8,889

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Fair Value of Investments Based upon Contractual Maturities (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Less than one year	$ 17,191	$ 18,290
Due in 1 - 5 years	7,117	9,821
Total	$ 24,308	$ 28,111

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) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers	$ 155,693	$ 93,294
Securities failed-to-deliver - customers	288,235	87,685
Deposits with clearing organizations and broker-dealers	111,594	97,043
Other	9,435	1,893
Total	564,957	279,915
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers	156,322	70,917
Securities failed-to-receive - customers	144,958	60,784
Other	6,988	1,625
Total	$ 308,268	$ 133,326

Acquisitions - Additional Infor

Acquisitions - Additional Information (Detail) - USD ($) $ in Millions	Apr. 09, 2021	Nov. 30, 2020
Regulatory Services GmbH of Deutsche Borse Group [Member]
Business Acquisition [Line Items]
Cash consideration		$ 22.5
Amortizable intangible assets		$ 37.4
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		$ 24.6
MuniBrokers LLC [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Cash consideration	$ 17
Business combination, contingent consideration payment period	2 years
MuniBrokers LLC [Member] | Maximum [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Contingent consideration payable	$ 25

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Goodwill [Line Items]
Amortization expense associated with identifiable intangible assets	$ 2.7	$ 0.7
Estimated total amortization expense on intangible assets 2021	5.7
Estimated total amortization expense on intangible assets 2022	6.9
Estimated total amortization expense on intangible assets 2023	7.9
Estimated total amortization expense on intangible assets 2024	6.7
Estimated total amortization expense on intangible assets 2025	5.7
Indefinite-lived Intangible Assets [Member]
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 147.4		$ 147.4

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Summary of Company's Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite Lived Intangible Assets [Line Items]
Cost	$ 107,512	$ 109,246
Accumulated amortization	(16,567)	(13,892)
Net carrying amount	90,945	95,354
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Cost	100,962	102,696
Accumulated amortization	(10,044)	(7,369)
Net carrying amount	90,918	95,327
Technology and Other Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Cost	6,550	6,550
Accumulated amortization	(6,523)	(6,523)
Net carrying amount	$ 27	$ 27

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Current:
Federal	$ 12,523	$ 7,766
State and local	3,411	2,910
Foreign	4,819	3,447
Total current provision	20,753	14,123
Deferred:
Federal	602	1,905
State and local	101	352
Foreign	(112)	506
Total deferred provision	591	2,763
Provision for income taxes	$ 21,344	$ 16,886
Effective tax rate	21.00%	18.40%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule Of Pre Tax Income [Line Items]
Excess tax benefits on share based payments	$ 4	$ 6.3
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

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 7,424	$ 6,677
Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	7,103	6,399
Non-Employee Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 321	$ 278

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Additional Information (Detail) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested | $	$ 50.9
Weighted-average period over which cost is expected to be recognized	2 years 2 months 12 days
Employees [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period | shares	32,251
Weighted-average grant date fair value per share | $ / shares	$ 526.50
Employees [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of non-option equity instruments granted during the period | shares	12,185
Number of stock option equity instruments granted during the period | shares	15,982
Weighted-average fair value each option granted | $ / shares	$ 138.51
Weighted-average grant date fair value per share | $ / shares	$ 523

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	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share Basic And Diluted [Abstract]
Basic weighted average shares outstanding	37,470	37,303
Dilutive effect of stock options and restricted stock	685	772
Diluted weighted average shares outstanding	38,155	38,075
Basic earnings per share	$ 2.15	$ 2.01
Diluted earnings per share	$ 2.11	$ 1.96

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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	61,089	62,964

Credit Agreements and Short-t_2

Credit Agreements and Short-term Financing - Additional Information (Detail)	Nov. 13, 2020USD ($)Extension_Option	Oct. 31, 2015USD ($)	Mar. 31, 2021USD ($)
U.K. [Member] | Subsidiaries [Member]
Line Of Credit Facility [Line Items]
Interest expense on short-term debt			$ 200,000
Accounts Payable, Accrued Expenses and Other Liabilities [Member] | U.K. [Member] | Subsidiaries [Member]
Line Of Credit Facility [Line Items]
Outstanding overdrafts payable			34,300,000
Collateralized Agreement [Member]
Line Of Credit Facility [Line Items]
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] | Maximum [Member]
Line Of Credit Facility [Line Items]
Interest expense on borrowings			$ 100,000
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
Expiration period of credit agreement		Nov. 13, 2020
Period of credit agreement	1 year
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			$ 0
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	3 Months Ended
	Mar. 31, 2021USD ($)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 | $	$ 1.7
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 Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease Cost [Line Items]
Net lease cost	$ 3,324	$ 3,465
Other, net [Member]
Lease Cost [Line Items]
Operating lease cost for subleased/assigned properties	497	536
Sublease income subleased/assigned properties	(502)	(536)
Occupancy [Member]
Lease Cost [Line Items]
Operating lease cost	3,323	3,449
Variable lease costs	$ 6	$ 16

Leases - Summary of Weighted Av

Leases - Summary of Weighted Average Remaining Lease Term and Discount Rate (Details)	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Weighted average remaining lease term (in years)	12 years	12 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	Mar. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Remainder of 2021	$ 9,177
2022	10,692
2023	10,451
2024	11,122
2025	11,127
2026 and thereafter	79,095
Total lease payments	131,664
Less: interest	38,914
Operating lease liabilities	$ 92,750	$ 93,612

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Settlement days of bond transaction	within one to two trading days

Share Repurchase Program - Addi

Share Repurchase Program - Additional Information (Detail) - Share Repurchase Program [Member] - USD ($)	1 Months Ended		3 Months Ended
	Jan. 31, 2021	Jan. 31, 2019	Mar. 31, 2021
Equity Class Of Treasury Stock [Line Items]
Total shares repurchased			1,050
Cost of common stock shares repurchased			$ 500,000
Shares repurchase program period		2 years
Shares repurchase program authorized	$ 100,000,000	$ 100,000,000
Commencement date		2019-04
Share repurchase program, expiration date		Mar. 31, 2021
Share repurchase program, commencement date	Apr. 1, 2021

Segment and Geographic Inform_3

Segment and Geographic Information - Additional Information (Detail) - Segment	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
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%

Segment and Geographic Inform_4

Segment and Geographic Information - Summary of Revenue and Long-lived Assets (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 195,464	$ 168,978
Long-lived assets	88,655		$ 85,204
Americas [Member]
Segment Reporting Information [Line Items]
Revenues	160,119	142,637
Long-lived assets	70,812		68,707
Europe [Member]
Segment Reporting Information [Line Items]
Revenues	29,544	22,419
Long-lived assets	17,838		16,491
Asia [Member]
Segment Reporting Information [Line Items]
Revenues	5,801	$ 3,922
Long-lived assets	$ 5		$ 6

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	Mar. 31, 2021	Dec. 31, 2020
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	$ 390,915	$ 460,858
Cash segregated under federal regulations	50,083	50,059
Deposits with clearing organizations and broker-dealers	111,594	97,043
Total	552,682	608,050
Cash and Cash Equivalents [Member]
Cash And Cash Equivalents [Line Items]
Cash and cash equivalents	390,915	460,858
Cash Segregated under Federal Regulations and Other [Member]
Cash And Cash Equivalents [Line Items]
Cash segregated under federal regulations	50,083	50,059
Receivables from Broker-Dealers, Clearing Organizations and Customers [Member]
Cash And Cash Equivalents [Line Items]
Deposits with clearing organizations and broker-dealers	111,594	97,043
Prepaid Expenses and Other Assets [Member]
Cash And Cash Equivalents [Line Items]
Other deposits	$ 90	$ 90