MarketAxess (MKTX) 10-K/A 23 Feb 18 2017 FY Annual report (amended) Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K/A
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	MKTX
Entity Registrant Name	MARKETAXESS HOLDINGS INC
Entity Central Index Key	1,278,021
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		37,629,246
Entity Public Float			$ 7.3

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 167,014	$ 168,243
Investments, at fair value	239,521	194,404
Accounts receivable, net of allowance of $178 and $82 as of December 31, 2017 and 2016, respectively	52,636	50,668
Goodwill and intangible assets, net of accumulated amortization	63,059	63,443
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	38,548	31,104
Prepaid expenses and other assets	18,717	11,618
Deferred tax assets, net	1,737	8,562
Total assets	581,232	528,042
Liabilities
Accrued employee compensation	36,502	34,783
Income and other tax liabilities	13,061	7,582
Deferred revenue	2,660	2,515
Accounts payable, accrued expenses and other liabilities	14,241	15,149
Total liabilities	66,464	60,029
Commitments and Contingencies (Note 12)
Stockholders' equity
Additional paid-in capital	331,081	342,311
Treasury stock - Common stock voting, at cost, 2,781,323 and 2,562,585 shares as of December 31, 2017 and 2016, respectively	(159,791)	(117,330)
Retained earnings	353,583	255,140
Accumulated other comprehensive loss	(10,226)	(12,228)
Total stockholders' equity	514,768	468,013
Total liabilities and stockholders' equity	581,232	528,042
Undefined Preferred Stock [Member]
Stockholders' equity
Preferred stock
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock
Voting Common Stock [Member]
Stockholders' equity
Common stock	$ 121	$ 120

Consolidated Statements of Fin3

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for accounts receivable	$ 178	$ 82
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	40,402,059	40,106,360
Common stock, shares outstanding	37,620,736	37,543,775
Treasury stock, shares	2,781,323	2,562,585
Series A Preferred Stock [Member]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	110,000	110,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock Non-Voting [Member]
Common stock, par value	$ 0.003	$ 0.003
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Commissions	$ 355,282	$ 332,307	$ 266,221
Information services	25,807	23,269	22,585
Post-trade services	11,090	10,812	11,648
Investment income	3,619	2,137	905
Other	1,673	1,394	1,739
Total revenues	397,471	369,919	303,098
Expenses
Employee compensation and benefits	102,751	96,785	83,856
Depreciation and amortization	19,274	17,838	18,542
Technology and communications	20,048	17,275	15,916
Professional and consulting fees	19,367	17,175	13,043
Occupancy	6,125	4,681	4,685
Marketing and advertising	9,762	8,934	6,148
Clearing costs	5,797	6,060	3,313
General and administrative	12,579	9,569	9,695
Total expenses	195,703	178,317	155,198
Income before income taxes	201,768	191,602	147,900
Provision for income taxes	53,679	65,430	51,863
Net income	$ 148,089	$ 126,172	$ 96,037
Net income per common share
Basic	$ 4.02	$ 3.42	$ 2.62
Diluted	3.89	3.34	2.55
Cash dividends declared per common share	$ 1.32	$ 1.04	$ 0.80
Weighted average shares outstanding
Basic	36,864	36,844	36,690
Diluted	38,038	37,738	37,637

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 148,089	$ 126,172	$ 96,037
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(2,807), $5,407 and $(258), respectively	2,236	(7,037)	(512)
Net unrealized (loss) gain on securities available-for-sale, net of tax of $(39), $24, and $(111), respectively	(234)	38	(180)
Comprehensive income	$ 150,091	$ 119,173	$ 95,345

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Foreign currency exchange hedge, tax expense (benefit)	$ (2,807)	$ 5,407	$ (258)
Securities available-for-sale, tax expense (benefit)	$ (39)	$ 24	$ (111)

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, 2014	$ 334,208	$ 120	$ 307,059	$ (70,247)	$ 101,813	$ (4,537)
Net income	96,037				96,037
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(512)					(512)
Unrealized net gain (loss) on securities available-for-sale, net of tax	(180)					(180)
Stock-based compensation	12,519		12,519
Exercise of stock options	1,824	1	1,823
Withholding tax payments on restricted stock vesting and stock option exercises	(4,496)		(4,496)
Excess tax benefits from stock-based compensation	4,310		4,310
Repurchases of common stock	(23,158)			(23,158)
Cash dividend on common stock	(29,839)				(29,839)
Ending Balance at Dec. 31, 2015	390,713	121	321,215	(93,405)	168,011	(5,229)
Net income	126,172				126,172
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	(7,037)					(7,037)
Unrealized net gain (loss) on securities available-for-sale, net of tax	38					38
Stock-based compensation	14,511		14,511
Exercise of stock options	2,299		2,299
Withholding tax payments on restricted stock vesting and stock option exercises	(5,173)	(1)	(5,172)
Excess tax benefits from stock-based compensation	9,458		9,458
Repurchases of common stock	(23,925)			(23,925)
Cash dividend on common stock	(39,043)				(39,043)
Ending Balance at Dec. 31, 2016	468,013	120	342,311	(117,330)	255,140	(12,228)
Net income	148,089				148,089
Cumulative translation adjustment and foreign currency exchange hedge, net of tax	2,236					2,236
Unrealized net gain (loss) on securities available-for-sale, net of tax	(234)					(234)
Stock-based compensation	14,421		14,421
Exercise of stock options	1,972	1	1,971
Withholding tax payments on restricted stock vesting and stock option exercises	(27,691)		(27,691)
Repurchases of common stock	(42,461)			(42,461)
Cumulative effect of change in accounting for employee share-based payments	17		69		(52)
Cash dividend on common stock	(49,594)				(49,594)
Ending Balance at Dec. 31, 2017	$ 514,768	$ 121	$ 331,081	$ (159,791)	$ 353,583	$ (10,226)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 148,089	$ 126,172	$ 96,037
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,274	17,838	18,542
Stock-based compensation expense	14,421	14,511	12,519
Deferred taxes	6,590	(2,581)	(2,424)
Other	1,953	10,628	6,359
Changes in operating assets and liabilities:
(Increase) in accounts receivable	(2,353)	(10,429)	(6,748)
(Increase) in prepaid expenses and other assets	(7,039)	(2,125)	(2,662)
Increase in accrued employee compensation	1,719	5,487	3,986
Increase (decrease) in income and other tax liabilities	5,770	3,221	(941)
Increase (decrease) in deferred revenue	145	203	(153)
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(1,614)	2,344	(9)
Net cash provided by operating activities	168,035	89,747	124,506
Cash flows from investing activities
Proceeds from maturities and sales, available-for-sale investments	187,794	46,347	35,248
Purchase, available-for-sale investments	(215,831)	(81,438)	(57,175)
Purchases of furniture, equipment and leasehold improvements	(12,086)	(6,385)	(4,795)
Capitalization of software development costs	(13,471)	(12,118)	(10,589)
Other	(59)	414	(642)
Net cash (used in) investing activities	(53,653)	(53,180)	(37,953)
Cash flows from financing activities
Cash dividend on common stock	(48,888)	(38,495)	(29,534)
Exercise of stock options	1,972	2,299	1,824
Withholding tax payments on restricted stock vesting and stock option exercises	(27,691)	(5,173)	(4,496)
Repurchases of common stock	(42,461)	(23,925)	(23,158)
Net cash (used in) financing activities	(117,068)	(65,294)	(55,364)
Effect of exchange rate changes on cash and cash equivalents	1,457	(2,758)	(385)
Cash and cash equivalents
Net (decrease) increase for the period	(1,229)	(31,485)	30,804
Beginning of period	168,243	199,728	168,924
End of period	167,014	168,243	199,728
Supplemental cash flow information:
Cash paid during the year for income taxes	43,997	58,268	$ 50,875
Corporate Debt [Member]
Changes in operating assets and liabilities:
(Increase) in trading securities	(17,081)	(74,195)
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
(Increase) in trading securities	$ (1,839)	$ (1,327)

Organization and Principal Busi

Organization and Principal Business Activity	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Organization and Principal Business Activity	1. Organization and Principal Business Activity MarketAxess Holdings Inc. (the “Company” or “MarketAxess”) was incorporated in the State of Delaware on April 11, 2000. Through its subsidiaries, MarketAxess operates a leading electronic trading platform that enables fixed-income market participants to efficiently trade corporate bonds and other types of fixed-income instruments using MarketAxess’ patented trading technology. Over 1,300 institutional investor and broker-dealer firms are active users of the MarketAxess trading platform, accessing global liquidity in U.S. high-grade corporate bonds, emerging markets and high-yield bonds, European bonds, U.S. agency bonds, municipal bonds, credit default swaps and other fixed-income securities. Through its Open Trading™ protocols, MarketAxess executes certain bond transactions 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 in trades which then settle through third-party clearing brokers. MarketAxess also offers a number of trading-related products and services, including: market data to assist clients with trading decisions; connectivity solutions that facilitate straight-through processing; technology services to optimize trading environments; and execution services for exchange-traded fund managers and other clients. Through its Trax ®

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
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. Cash and Cash Equivalents Cash and cash equivalents includes cash and money market instruments that are primarily maintained at one major global bank. Given this concentration, the Company is exposed to certain credit risk in relation to its deposits at this bank. The Company defines cash equivalents as short-term interest-bearing investments with maturities at the time of purchase of three months or less. Investments The Company determines the appropriate classification of securities at the time of purchase which are recorded in the Consolidated Statements of Financial Condition on the trade date. Securities are classified as available-for-sale or trading. The Company’s available-for-sale investments are comprised of municipal bonds and investment grade corporate debt securities. Available-for-sale investments are carried at fair value with the unrealized gains or losses reported in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Trading investments primarily include investment grade corporate debt securities and are carried at fair value, with realized and unrealized gains or losses included in other income in the Consolidated Statements of Operations. The Company assesses whether an other-than-temporary impairment loss on the available-for-sale investments has occurred due to declines in fair value or other market conditions. The portion of an other-than-temporary impairment related to credit loss is recorded as a charge in the Consolidated Statements of Operations. The remainder is recognized in accumulated other comprehensive loss if the Company does not intend to sell the security and it is more likely than not that the Company will not be required to sell the security prior to recovery. No charges for other-than-temporary losses were recorded during the years ended December 31, 2017, 2016 and 2015. 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. Allowance for Doubtful Accounts 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 doubtful accounts is based upon the historical collection experience and specific collection issues that have been identified. Additions to the allowance for doubtful accounts are charged to bad debt expense, which is included in general and administrative expense in the Company’s Consolidated Statements of Operations. The allowance for doubtful accounts was $0.2 million, $0.1 million and $0.1 million as of December 31, 2017, 2016 and 2015, respectively. The provision for bad debts was $0.4 million, $0.2 million and $0.2 million for the years ended December 31, 2017, 2016 and 2015, respectively. Write-offs and other charges against the allowance for doubtful accounts were $0.1 million for each year ended December 31, 2017, 2016 and 2015, respectively. Depreciation and Amortization Fixed assets are carried at cost less accumulated depreciation. The Company uses the straight-line method of depreciation over three to seven years. The Company amortizes leasehold improvements on a straight-line basis over the lesser of the life of the improvement or the remaining term of the lease. Software Development Costs The Company capitalizes certain costs associated with the development of internal use software, including among other items, employee compensation and related benefits and third party consulting costs at the point at which the conceptual formulation, design and testing of possible software project alternatives have been completed. Once the product is ready for its intended use, such costs are amortized on a straight-line basis over three years. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Cash Provided as Collateral Cash is provided as collateral for broker-dealer clearing accounts. Cash provided as collateral is included in prepaid expenses and other assets in the Consolidated Statements of Financial Condition. 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 general and administrative expense 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 majority of the Company’s revenues are derived from commissions for trades executed on its platform and distribution fees that are billed to its broker-dealer clients on a monthly basis. The Company also derives revenues from information and post-trade services, technology products and services, investment income and other income. Commission revenue. Commissions are generally calculated as a percentage of the notional dollar volume of bonds traded on the platform and vary based on the type, size, yield and maturity of the bond traded. Under the Company’s transaction fee plans, bonds that are more actively traded or that have shorter maturities are generally charged lower commissions, while bonds that are less actively traded or that have longer maturities generally command higher commissions. For 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 the commission through the difference in price between the two matched principal trades. Fee programs for certain products include distribution fees which are recognized monthly. Information Services. The Company generates revenue from data licensed to its broker-dealer clients, institutional investor clients and data-only subscribers, professional consulting services, technology software licenses and maintenance and support services. Information service revenues are invoiced monthly, quarterly or annually. When billed in advance, information service revenues are deferred and recognized monthly on a straight-line basis. Revenue from professional consulting services are recognized as services are performed and software license subscription revenue and maintenance and support services are recognized ratably over the contract period. Post-trade Services . The Company generates revenue from regulatory transaction reporting, trade publication and trade matching services. Revenue is recognized in the period the services are provided. 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. Effective upon the Company’s adoption of ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”) on January 1, 2017, the Company accounts for forfeitures as they occur. Prior to the adoption of ASU 2016-09, expected forfeitures were included in determining share-based compensation expense. 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 general and administrative expenses in the Consolidated Statements of Operations. Effective upon the Company’s adoption of ASU 2016-09 all tax effects related to share-based payments are recorded through tax expense in the periods during which the awards are exercised or vest. On December 22, 2017, the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”) to address the application of U.S. generally accepted accounting principles (“GAAP”) related to the enactment of the Tax Cuts and Jobs Act (the “Tax Act”). SAB 118 allows the Company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The measurement period ends when the Company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. The Company expects to complete its analysis within the measurement period in accordance with SAB 118. Business Combinations, Goodwill and Intangible Assets Business combinations are accounted for under the purchase method of accounting. The total cost of an acquisition is allocated to the underlying net assets based on their respective estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Determining the fair value of certain assets acquired and liabilities assumed is judgmental in nature and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth rates and asset lives. The Company operates as a single reporting unit. Subsequent to 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 on a straight-line basis over their estimated useful lives, ranging from three to 15 years. 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. Out-of-Period Adjustments During the first quarter of 2016, the Company determined that it had incorrectly recorded deferred taxes for the cumulative translation adjustment (“CTA”) that arises from converting the local currency financial statements into U.S. dollars. Upon making a permanent reinvestment assertion on unremitted earnings from foreign subsidiaries effective January 1, 2013, the Company should have eliminated any deferred tax balances derived from the CTA balance. The Company also determined that gains and losses on the foreign currency forward contracts used to hedge the net investment in certain foreign subsidiaries were not appropriately considered as taxable income or expense in the consolidated tax returns. The Company assessed these errors and determined that they were not material to previous reporting periods. Therefore, the Company recorded these items as out-of-period adjustments in the three months ended March 31, 2016 by decreasing deferred tax assets by $3.1 million, decreasing other comprehensive income by $2.1 million and increasing prepaid expenses and other assets by $1.0 million in the Consolidated Statements of Financial Condition. Reclassifications Certain reclassifications have been made to the prior years’ Consolidated Financial Statements in order to conform to the current year presentation. The Company reclassified certain revenue line items on the consolidated statements of operations to separately reflect information service revenues and post-trade service revenues. Such reclassifications had no effect on previously reported net income. Accounting Pronouncements, Recently Adopted Effective January 1, 2017, the Company adopted ASU 2016-09 which simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, statutory tax withholding requirements and classification on the statement of cash flows. Beginning January 1, 2017, the tax effects related to share-based payments are recorded through the income tax provision and the Company has elected to account for forfeitures as they occur. The adoption of ASU 2016-09 will cause volatility in the Company’s net income, effective tax rate and diluted earnings per share. The volatility in future periods will depend on the Company’s stock price at the vesting date for restricted stock awards or exercise date for stock options and the number of awards that vest or are exercised in each period. Under the new guidance, excess tax benefits from share-based compensation are included as an operating activity in the Company’s Consolidated Statements of Cash Flows. Prior period cash flows have been adjusted to conform to the new presentation. Accounting Pronouncements, Not Yet Adopted as of December 31, 2017 In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”) requiring an entity to recognize revenue for the transfer of goods or services equal to the amount that it expects to be entitled to receive for those goods or services. The standard also requires new disclosure concerning contracts with customers, including the significant judgments made when applying the guidance. The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective transition approach. The Company completed its analysis and the adoption of this guidance will not have a material impact on the Company’s Consolidated Financial Statements. In February 2016, the FASB issued ASU 2016-02, “Leases” (“ASU 2016-02”) requiring lessees to recognize lease assets and lease liabilities on the balance sheet for those leases previously classified as operating leases. ASU 2016-02 will be effective for the Company beginning January 1, 2019 and early adoption is permitted and should be applied prospectively. The Company is currently evaluating the potential adoption impact and expects to recognize lease assets and lease liabilities in its Consolidated Statements of Financial Condition. The Company does not expect material changes to the recognition of operating lease expense in its Consolidated Statements of Operations. In January 2017, the FASB issued ASU 2017-04, “Intangibles-Goodwill and Other” (“ASU 2017-04”). ASU 2017-04 simplifies the testing for goodwill impairment. The guidance will be effective for the Company beginning January 1, 2020 and early adoption is permitted and should be applied prospectively. The adoption of this guidance is not expected to have a material effect on the Company’s Consolidated Financial Statements.

Net Capital Requirements

Net Capital Requirements	12 Months Ended
	Dec. 31, 2017
Net Capital [Abstract]
Net Capital Requirements	3. Net Capital Requirements Certain U.S. subsidiaries of the Company are registered as a broker-dealer or swap execution facility and therefore are subject to the applicable rules and regulations of the Securities and Exchange Commission and the Commodity Futures Trading Commission. These rules contain minimum net capital requirements, as defined in the applicable regulations, and also may require a significant part of the registrants’ assets be kept in relatively liquid form. Certain of the Company’s foreign subsidiaries are regulated by the Financial Conduct Authority in the U.K. or other foreign regulators and must maintain financial resources, as defined in the applicable regulations, in excess of the applicable financial resources requirement. As of December 31, 2017, each of the Company’s subsidiaries that are subject to these regulations had net capital or financial resources in excess of their minimum requirements. As of December 31, 2017, the Company’s subsidiaries maintained aggregate net capital and financial resources that was $130.5 million in excess of the required levels of $14.8 million. Each of the Company’s U.S. and foreign regulated subsidiaries are subject to local regulations which generally prohibit repayment of borrowings from the Company or affiliates, paying cash dividends, making loans to the Company or affiliates or otherwise entering into transactions that result in a significant reduction in regulatory net capital or financial resources without prior notification to or approval from such regulated entity’s principal regulator.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2. Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2017 Money market funds $ 88,562 $ — $ — $ 88,562 Securities available-for-sale Corporate debt — 145,052 — 145,052 Trading securities Corporate debt — 91,302 — 91,302 Mutual funds held in rabbi trust — 3,167 — 3,167 Foreign currency forward position — (702 ) — (702 ) Total $ 88,562 $ 238,819 $ — $ 327,381 As of December 31, 2016 Money market funds $ 58,573 $ — $ — $ 58,573 Securities available-for-sale Corporate debt — 118,870 — 118,870 Trading securities Corporate debt — 74,207 — 74,207 Mutual funds held in rabbi trust — 1,327 — 1,327 Foreign currency forward position — (266 ) — (266 ) Total $ 58,573 $ 194,138 $ — $ 252,711 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 deferred cash incentive plan (see Note 14). There were no financial assets classified within Level 3 during the years ended December 31, 2017 and 2016. 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 period and are used to limit exposure to foreign currency exchange rate fluctuations. The fair value of the asset is included in prepaid expenses and other assets and the fair value of the liability is included in accounts payable, accrued expenses and other liabilities in the Consolidated Statements of Financial Condition. Gains or losses on foreign currency forward contracts designated as hedges are included in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. A summary of the foreign currency forward position is as follows: As of December 31, 2017 2016 (In thousands) Notional value $ 84,422 $ 66,972 Fair value of notional 85,124 67,238 Fair value of the (liability) $ (702 ) $ (266 ) The following is a summary of the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value (In thousands) As of December 31, 2017 Securities available-for-sale Corporate debt $ 145,526 $ 9 $ (483 ) $ 145,052 Trading securities Corporate debt 91,578 30 (306 ) 91,302 Mutual funds held in rabbi trust 2,729 438 — 3,167 Total trading securities 94,307 468 (306 ) 94,469 Total investments $ 239,833 $ 477 $ (789 ) $ 239,521 As of December 31, 2016 Securities available-for-sale Corporate debt $ 119,073 $ 13 $ (216 ) $ 118,870 Trading securities Corporate debt 74,394 47 (234 ) 74,207 Mutual funds held in rabbi trust 1,212 115 — 1,327 Total trading securities 75,606 162 (234 ) 75,534 Total investments $ 194,679 $ 175 $ (450 ) $ 194,404 The following table summarizes the fair value of the investments based upon the contractual maturities: As of December 31, 2017 2016 (In thousands) Less than one year $ 130,738 $ 117,904 Due in 1 - 5 years 108,783 76,500 Total $ 239,521 $ 194,404 Proceeds from the sales and maturities of investments during the years ended December 31, 2017, 2016 and 2015 were $219.2 million, $69.5 million and $35.2 million, respectively. For the years ended December 31, 2017 and 2016, net unrealized losses on corporate debt trading securities were $0.1 million and $0.2 million, respectively. For the years ended December 31, 2017 and 2016, net realized gains on corporate debt trading securities were immaterial. The following table provides fair values and unrealized losses on investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2017 and 2016 respectively: Less than Twelve Months Twelve Months or More Total Estimated fair value Gross unrealized losses Estimated fair value Gross unrealized losses Estimated fair value Gross unrealized losses (In thousands) As of December 31, 2017 Corporate debt $ 177,114 $ (536 ) $ 26,476 $ (253 ) $ 203,590 $ (789 ) As of December 31, 2016 Corporate debt $ 136,667 $ (449 ) $ 2,000 $ (1 ) $ 138,667 $ (450 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	5. Goodwill and Intangible Assets Goodwill and intangible assets with indefinite lives was $59.7 million as of both December 31, 2017 and 2016. Intangible assets that are subject to amortization, including the related accumulated amortization, are comprised of the following: December 31, 2017 December 31, 2016 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Technology $ 5,770 $ (5,770 ) $ — $ 5,770 $ (5,770 ) $ — Customer relationships 5,647 (2,301 ) 3,346 5,628 (1,897 ) 3,731 Non-competition agreements 380 (380 ) — 380 (380 ) — Tradenames 370 (370 ) — 370 (370 ) — Total $ 12,167 $ (8,821 ) $ 3,346 $ 12,148 $ (8,417 ) $ 3,731 Amortization expense associated with identifiable intangible assets was $0.4 million, $0.7 million and $2.3 million, respectively, for the years ended December 31, 2017, 2016 and 2015. Estimated total amortization expense is

Capitalized Software, Furniture

Capitalized Software, Furniture, Equipment and Leasehold Improvements	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Capitalized Software, Furniture, Equipment and Leasehold Improvements	6. Capitalized Software, Furniture, Equipment and Leasehold Improvements Capitalized software development costs, furniture, equipment and leasehold improvements, net of accumulated depreciation and amortization, are comprised of the following: As of December 31, 2017 2016 (In thousands) Software development costs $ 86,129 $ 71,551 Computer hardware and related software 35,945 20,152 Office hardware 4,575 4,228 Furniture and fixtures 2,347 2,001 Leasehold improvements 11,016 8,351 140,012 106,283 Accumulated depreciation and amortization (101,464 ) (75,179 ) Total $ 38,548 $ 31,104 During the years ended December 31, 2017 and 2016, software development costs totaling $13.9 million and $12.3 million, respectively, were capitalized. Non-capitalized software costs and routine maintenance costs are expensed as incurred and are included in employee compensation and benefits and professional and consulting fees in the Consolidated Statements of Operations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The provision for income taxes consists of the following: Year Ended December 31, 2017 2016 2015 (In thousands) Current: Federal $ 36,045 $ 45,455 $ 38,357 State and local 3,848 7,087 7,180 Foreign 7,234 6,166 4,346 Total current provision 47,127 58,708 49,883 Deferred: Federal 6,171 5,884 1,492 State and local 661 1,141 299 Foreign (280 ) (303 ) 189 Total deferred provision 6,552 6,722 1,980 Provision for income taxes $ 53,679 $ 65,430 $ 51,863 Pre-tax income from U.S. operations was $165.2 million, $161.9 million and $126.4 million for the years ended December 31, 2017, 2016 and 2015, respectively. Pre-tax income from foreign operations was $36.6 million, $29.7 million and $21.5 million for the years ended December 31, 2017, 2016 and 2015, respectively. On December 22, 2017, the Tax Act was enacted into law. The Tax Act significantly revises the U.S. corporate income tax regime by, among other things, lowering the U.S. federal corporate income tax rate from 35% to 21%, implementing a territorial tax system and imposing a repatriation tax on deemed earnings of foreign subsidiaries. The Company has made a reasonable estimate of the impact of the Tax Act and recorded a provisional tax charge in 2017 of $11.7 million, composed of $6.7 million to re-measure U.S. deferred tax assets and $5.0 million for the repatriation tax on accumulated undistributed foreign earnings. The final impact of the Tax Act may differ materially from the provisional tax charge recognized in 2017 due to, among other things, changes in interpretations and assumptions the Company has made, guidance that may be issued by the U.S. Department of Treasury and actions the Company may take as a result of the Tax Act. Pursuant to the Tax Act, all previously undistributed foreign earnings have now been subject to U.S. tax. Notwithstanding the U.S. taxation of these amounts, the Company considers its undistributed foreign earnings to be indefinitely reinvested outside of the U.S. and does not expect to incur any significant additional taxes related to such amounts. The difference between the Company’s reported provision for income taxes and the U.S. federal statutory rate of 35% is as follows: Year Ended December 31, 2017 2016 2015 U.S. federal tax at statutory rate 35.0 % 35.0 % 35.0 % State and local taxes - net of federal benefit 1.5 2.9 3.4 Credits and deductions related to research activities (1.2 ) (1.3 ) (1.3 ) Foreign rate differential benefit (2.9 ) (2.3 ) (2.0 ) Excess tax benefit from stock-based compensation (11.6 ) — — Tax Cuts and Jobs Act provisional tax charge 5.8 — — Other, net — (0.2 ) — Provision for income taxes 26.6 % 34.1 % 35.1 % The following is a summary of the Company’s net deferred tax assets: As of December 31, 2017 2016 (In thousands) Deferred tax assets: U.S. net operating loss carryforwards $ 872 $ 1,909 Capital loss carryforwards 4,648 7,235 Stock compensation expense 4,534 11,307 Other 1,143 1,468 Total deferred tax assets 11,197 21,919 Valuation allowance (4,648 ) (7,235 ) Net deferred tax assets 6,549 14,684 Deferred tax liabilities: Depreciation and amortization (1,369 ) (1,456 ) Capitalized software development costs (3,479 ) (4,923 ) Intangible assets (967 ) (1,037 ) Deferred tax assets, net $ 734 $ 7,268 In 2001 and 2000, MarketAxess Holdings Inc. and MarketAxess Corporation had an ownership change within the meaning of Section 382 of the Internal Revenue Code. As of December 31, 2017, the Company had restricted U.S. federal net operating loss carryforwards of approximately $4.2 million related to the prior ownership change, which begin to expire in 2021. The Company’s net operating loss carryforwards may be subject to additional annual limitations if there is a 50% or greater change in the Company’s ownership, as determined over a rolling three-year period. The ultimate realization of deferred income tax assets is dependent upon the generation of future taxable income during the periods in which the temporary differences become deductible. If it is not more likely than not that some portion or all of the gross deferred income tax assets will be realized in future years, a valuation allowance is recorded. As of December 31, 2017, the valuation allowance relates to certain capital loss carryforwards that are not expected to be realized. In October 2013, the Company recognized a $20.6 million capital loss on the sale of Greenline Financial Technologies, Inc. of which $1.2 million was carried back or otherwise utilized against current period capital gains. A full valuation allowance was provided against the remaining capital loss carryforward. A summary of the changes in the valuation allowance is as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Valuation allowance at beginning of year $ 7,235 $ 7,294 $ 7,428 (Decrease) to valuation allowance attributable to: Federal and state tax rate changes (2,587 ) (59 ) (134 ) Valuation allowance at end of year $ 4,648 $ 7,235 $ 7,294 The Company or one of its subsidiaries files U.S. federal, state and foreign income tax returns. Income tax returns for U.S. Federal (through 2013), New York City (through 2003) and State (through 2009) and Connecticut State (through 2003) have been audited. An examination of the Company’s New York State income tax returns for 2010 through 2013 is currently underway. The Company cannot estimate when the examination will conclude or the impact such examinations will have on the Company’s Consolidated Financial Statements, if any. A reconciliation of the unrecognized tax benefits is as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Balance at beginning of year $ 29 $ 265 $ 265 Additions attributable to state and local apportionment 2,650 — — Reductions for tax positions of prior years (29 ) (236 ) — Balance at end of year $ 2,650 $ 29 $ 265

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity Common Stock As of December 31, 2017 and 2016, the Company had 110,000,000 authorized shares of voting common stock and 10,000,000 authorized shares of non-voting common stock. Voting common stock entitles the holder to one vote per share of common stock held. The following is a summary of the change in the Company’s outstanding shares of voting common stock: Year Ended December 31, 2017 2016 2015 (In thousands) Outstanding shares of voting common stock at the beginning of year 37,544 37,409 37,319 Exercise of stock options 262 181 183 Issuance of restricted stock, net of shares withheld for withholding tax payments and cancellations 39 104 178 Repurchases (224 ) (150 ) (271 ) Outstanding shares of voting common stock at the end of year 37,621 37,544 37,409 In January 2016, the Board of Directors authorized a two-year share repurchase program for up to $25.0 million of the Company’s common stock. In October 2016, the Board of Directors approved a $50.0 million increase in the size of the repurchase program. This share repurchase plan was terminated in September 2017 and the Board of Directors authorized a new fifteen-month share repurchase program for up to $100.0 million that commenced in October 2017. Shares repurchased under each program will be held in treasury for future use. Dividends During 2017, 2016 and 2015, the Company paid quarterly cash dividends of $0.33 per share, $0.26 per share and $0.20 per share, respectively. Any future declaration and payment of dividends will be at the sole discretion of the Company’s Board of Directors. The Board of Directors may take into account such matters as general business conditions, the Company’s financial results, capital requirements, contractual obligations, legal, and regulatory restrictions on the payment of dividends to the Company’s stockholders or by the Company’s subsidiaries to their respective parent entities, and any such other factors as the Board of Directors may deem relevant.

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Plans	9. Stock-Based Compensation Plans The Company has a stock incentive plan which provides for the grant of stock options, stock appreciation rights, restricted stock, performance shares, performance units, or other stock-based awards as incentives and rewards to encourage employees, consultants and non-employee directors to participate in the long-term success of the Company. As of December 31, 2017, there were 219,983 shares available for grant under the stock incentive plan. Total stock-based compensation expense was as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Employees: Restricted stock and performance shares $ 11,566 $ 12,459 $ 10,792 Stock options 1,882 1,143 826 13,448 13,602 11,618 Non-employee directors: Restricted stock 973 909 901 Total stock-based compensation $ 14,421 $ 14,511 $ 12,519 The Company records stock-based compensation expense for employees in employee compensation and benefits and for non-employee directors in general and administrative expenses in the Consolidated Statements of Operations. Stock Options The exercise price of each option granted is equal to the market price of the Company’s common stock on the date of grant. Generally, option grants have provided for vesting over a three or five-year period. Options generally expire in six or ten years from the date of grant. The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model. The determination of fair value of share-based payment awards on the date of grant using an option-pricing model is affected by the Company’s stock price as well as assumptions regarding a number of highly complex and subjective variables, including the expected stock price volatility over the term of the awards, the risk-free interest rate, the expected dividend yield rate and the expected term. Expected volatilities are based on historical volatility of the Company’s stock. The risk-free interest rate is based on U.S. Treasury securities with a maturity value approximating the expected term of the option. The dividend yield rate is based on the expected annual dividends to be paid divided by the expected stock price. The expected term represents the period of time that options granted are expected to be outstanding based on actual and projected employee stock option exercise behavior. The weighted-average fair value for options granted during 2017, 2016 and 2015 was $40.08, $32.24 and $36.46, respectively. The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted for the three years ended December 31, 2017: 2017 2016 2015 Expected life (years) 5.0 6.0 7.0 Risk-free interest rate 1.9 % 1.9 % 1.9 % Expected volatility 28.0 % 33.0 % 56.7 % Expected dividend yield 0.8 % 1.0 % 1.1 % In addition to the option grants above, the Company granted 119,981 stock options to the Company’s Chief Executive Officer in January 2015 which expire in 5.5 years from the grant date. Subject to the Chief Executive Officer’s continued employment with the Company through the applicable vesting date, one-third of the options under the option award will vest and become exercisable on each of January 15, 2018, 2019 and 2020. The fair value of the option award as of the date of the grant was $2.0 million as determined by an independent third party using a Monte Carlo simulation model. Key assumptions used for the Monte Carlo pricing model included an exercise price of $88.25 (125% of the market price on the date of the grant), a risk free interest rate of 1.4%, volatility of 27.3% and a dividend yield of 0.9%. The following table reports stock option activity during the three years ended December 31, 2017 and the intrinsic value as of December 31, 2017: Number of Shares Weighted-Average Exercise Price ($) Remaining Contractual Term Intrinsic Value ($) (In thousands) Outstanding at December 31, 2014 1,014,420 $ 13.81 Granted 120,650 88.15 Canceled — — Exercised (196,034 ) 11.60 Outstanding at December 31, 2015 939,036 23.83 Granted 112,988 102.40 Canceled (874 ) 101.77 Exercised (195,410 ) 12.35 Outstanding at December 31, 2016 855,740 36.80 Granted 54,838 156.85 Canceled — — Exercised (380,967 ) 11.26 $ 68,068 Outstanding at December 31, 2017 529,611 67.60 3.3 71,046 Exercisable at December 31, 2017 254,079 24.61 3.0 45,009 The intrinsic value is the amount by which the closing price of the Company’s common stock on December 31, 2017 of $201.75 or the price on the day of exercise exceeds the exercise price of the stock options multiplied by the number of shares. As of December 31, 2017, there was $4.3 million of total unrecognized compensation cost related to non-vested stock options. That cost is expected to be recognized over a weighted-average period of 2.2 years. Restricted Stock and Performance Shares Restricted stock generally vests over a three or five-year period. Compensation expense is measured at the grant date and recognized ratably over the vesting period. Annual performance share awards are granted to certain officers and senior managers. Each performance share award is earned or forfeited based on the level of achievement by the Company of pre-tax operating income, as defined. The pay-out ranges from zero to 150% of the performance share award. For each performance share earned, a participant is awarded an equal number of shares of restricted stock. Any restricted stock awarded to a participant vests and ceases to be restricted stock in two equal installments on each of the second and third anniversaries of the date of grant of the applicable performance share award. Compensation expense for performance shares is measured at the grant date and recognized on a graded basis over the vesting period. Performance year: 2017 2016 2015 Share pay-out plan 12,971 15,390 28,520 Actual share pay-out in following year 8,094 21,423 37,696 Weighted average fair value per share on grant date $ 155.53 $ 101.77 $ 70.60 On April 1, 2017, the Company granted 9,367 multi-year performance shares to a certain officer. The performance share awards are earned or forfeited based on attaining certain cumulative operating income thresholds of the Company and select subsidiaries over the two-year period beginning January 1, 2017. The pay-out ranges from zero to 150% of the performance award value. Any restricted stock awarded will vest 50% on April 1, 2020 and 50% on April 1, 2021. The fair value per share of the awards on the grant date was $186.74. In January 2016, the Company granted 33,509 multi-year performance shares to certain officers and senior managers. Each performance share award is earned or forfeited based on the level of achievement by the Company of aggregate operating income over the three-year period beginning January 1, 2016. The pay-out ranges from zero to 150% of the performance award value. Any restricted stock awarded will vest 50% on January 31, 2020 and 50% on January 31, 2021. The fair value per share of the awards on the grant date was $103.30. In addition to the grants above, the Company granted 116,659 performance shares to the Company’s Chief Executive Officer in January 2015. The performance share award provided that the number of performance shares earned by the Chief Executive Officer would be based on the Company’s achievement of certain performance levels. Upon achievement of the performance levels, a total of 92,419 shares and . The following table reports restricted stock and performance share activity during the three years ended December 31, 2017: Number of Restricted Shares Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 435,989 $ 41.83 Granted 117,668 Performance share pay-out 117,647 Canceled (3,845 ) Vested (235,321 ) Outstanding at December 31, 2015 432,138 $ 56.24 Granted 95,419 Performance share pay-out 61,936 Canceled (12,786 ) Vested (192,729 ) Outstanding at December 31, 2016 383,978 $ 71.50 Granted 61,434 Performance share pay-out 21,422 Canceled (4,590 ) Vested (142,645 ) Outstanding at December 31, 2017 319,599 $ 88.77 As of December 31, 2017, there was $18.6 million of total unrecognized compensation expense related to non-vested restricted stock and performance shares. That cost is expected to be recognized over a weighted-average period of 1.7 years. Employee Stock Purchase Plan During 2015, the Company established a non-qualified employee stock purchase plan for non-executive employees. Under the plan, participants are granted the right to purchase shares of common stock based on the fair market value on the last day of the six-month offering period. On the purchase date, the Company will grant to the participants a number of shares of common stock equal to 20% of the aggregate shares purchased by the participant. These matching shares vest over a one-year period. The Company issued 1,034 and 1,190 matching shares in connection with the plan for the years ended December 31, 2017 and 2016, respectively. No matching shares were issued for the year ended December 31, 2015.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	10. Earnings Per Share The following table sets forth the computation of basic and diluted earnings per common share: Year Ended December 31, 2017 2016 2015 (In thousands, except per share amounts) Net income $ 148,089 $ 126,172 $ 96,037 Basic weighted average shares outstanding 36,864 36,844 36,690 Dilutive effect of stock options and restricted stock 1,174 894 947 Diluted weighted average shares outstanding 38,038 37,738 37,637 Basic earnings per share $ 4.02 $ 3.42 $ 2.62 Diluted earnings per share $ 3.89 $ 3.34 $ 2.55 Stock options and restricted stock totaling 31,766 shares, 84,052 shares and 128,383 shares for the years ended December 31, 2017, 2016 and 2015, respectively, were excluded from the computation of diluted earnings per share because their effect would have been antidilutive. The computation of diluted shares can vary among periods due, in part, to the change in the average price of the Company’s common stock.

Credit Agreement

Credit Agreement	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Credit Agreement	11. Credit Agreement In October 2015, the Company entered into a two-year amended and restated credit agreement (the “Credit Agreement”) that provided for revolving loans and letters of credit up to an aggregate of $100.0 million. The Company amended the Credit Agreement in October 2017 and extended the maturity date to October 2018. The amended Credit Agreement also provides for two additional one-year extension options and modified certain borrowing terms and covenants. Subject to satisfaction of certain specified conditions, the Company is permitted to upsize the borrowing capacity under the Credit Agreement by an additional $50.0 million. As of December 31, 2017, the Company had $0.9 million in letters of credit outstanding and $99.1 million in available borrowing capacity under the Credit Agreement. 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 satisfies certain covenants, which includes leverage ratios and minimum earnings before interest, tax, depreciation and amortization (“EBITDA”) requirements. The Company was in compliance with all applicable covenants at December 31, 2017 and December 31, 2016. The Company’s existing and future domestic subsidiaries (other than any regulated subsidiary) have guaranteed the Company’s obligations under the Credit Agreement. Subject to customary exceptions and exclusions, the Company’s borrowings under the Credit Agreement are collateralized by first priority pledges (subject to permitted liens) of substantially all of the Company’s personal property assets and the personal property assets of the Company’s domestic subsidiaries that have guaranteed the Credit Agreement, including the equity interests of the Company’s domestic subsidiaries and the equity interests of certain of the Company’s foreign subsidiaries (limited, in the case of the voting equity interests of the foreign subsidiaries, to a pledge of 65% of those equity interests). If an event of default occurs, including failure to pay principal or interest due on the loan balance, a voluntary or involuntary proceeding seeking liquidation, change in control of the Company, or one or more material judgments against the Company in excess of $10.0 million, the lenders would be entitled to accelerate the borrowings under the Credit Agreement and take various other actions, including all actions permitted to be taken by a secured creditor. If certain bankruptcy events of default occur, the borrowings under the Credit Agreement will automatically accelerate.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies Lease Commitments The Company leases office space under non-cancelable lease agreements expiring at various dates through 2033. Office space leases are subject to escalation based on certain costs incurred by the landlord. Minimum rental commitments as of December 31, 2017 under such operating leases were as follows (in thousands): 2018 $ 5,000 2019 9,659 2020 10,770 2021 10,149 2022 9,129 2023 and thereafter 99,166 $ 143,873 Rental expense for the years ended December 31, 2017, 2016 and 2015 was $5.3 million, $4.0 million and $4.1 million, respectively, and is included in occupancy expense in the Consolidated Statements of Operations. Rental expense has been recorded based on the total minimum lease payments after giving effect to rent abatement and concessions, which are being amortized on a straight-line basis over the life of the lease. The Company is contingently obligated for standby letters of credit amounting to $0.9 million that were issued to landlords for office space. During 2016, the Company entered into a lease agreement for its new global headquarters in New York City. The Company expects to relocate its headquarters to approximately 83,000 square feet of newly built office space at 55 Hudson Yards upon the building’s completion in late 2018. Rent expense recognition commenced upon acceptance of the premises in January 2018. The Company has assigned a lease agreement on a leased property to a third party and is contingently liable should the assignee default on future lease obligations through the November 2020 lease termination date. The aggregate amount of the future lease obligation under this arrangement is $0.8 million as of December 31, 2017. Legal In the normal course of business, the Company and its subsidiaries included in the consolidated financial statements may be involved in various lawsuits, proceedings and regulatory examinations. The Company assesses its liabilities and contingencies in connection with outstanding legal proceedings, if any, utilizing the latest information available. For matters where it is probable that the Company will incur a material loss and the amount can be reasonably estimated, the Company would establish an accrual for the loss. Once established, the accrual would be adjusted to reflect any relevant developments. When a loss contingency is not both probable and estimable, the Company does not establish an accrual. Based on currently available information, the outcome of the Company’s outstanding matters is not expected to have a material adverse impact on the Company’s financial position. It is not presently possible to determine the ultimate exposure to these matters and there is no assurance that the resolution of the outstanding matters will not significantly exceed any reserves accrued by the Company. Other The Company, through two regulated subsidiaries, executes certain bond transactions 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 in trades which settle through third-party clearing brokers. Settlement typically occurs within one to two trading days after the trade date. Cash settlement of the transaction occurs upon receipt or delivery of the underlying instrument that was traded. For the years ended December 31, 2017, 2016 and 2015, revenues from matched principal trading were approximately $45.7 million, $37.7 million and $16.9 million, respectively. Under securities clearing agreements with third party clearing brokers, the Company maintains collateral deposits with each clearing broker in the form of cash. As of December 31, 2017 and 2016, the amount of the collateral deposits included in prepaid expenses and other assets in the Consolidated Statements of Financial Condition was $1.2 million and $1.1 million, respectively. For the years ended December 31, 2017, 2016 and 2015, clearing expenses associated with matched principal transactions were $5.8 million, $6.1 million and $3.3 million, respectively, and are classified under clearing costs on the Consolidated Statements of Operations. The Company is exposed to credit risk in the event a counterparty does not fulfill its obligation to complete a transaction or if there is a miscommunication or other error in executing a matched principal transaction. Pursuant to the terms of the securities clearing agreements, each third-party clearing broker has the right to charge the Company for any losses they suffer resulting from a counterparty’s failure on any of the Company’s trades. The Company did not record any liabilities or losses with regard to this right for the years ended December 31, 2017 and 2016. In the normal course of business, the Company enters into contracts that contain a variety of representations, warranties and general indemnifications. The Company’s maximum exposure under these arrangements is unknown, as this would involve future claims that may be made against the Company that have not yet occurred. However, based on experience, the Company expects the risk of loss to be remote.

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment and Geographic Information	13. Segment and Geographic Information The Company operates an electronic multi-party platform for the trading of fixed-income securities and provides related data, analytics, compliance tools and post-trade services. The Company’s operations constitute a single business segment because of the highly integrated nature of these product and services, of the financial markets in which the Company competes and of the Company’s worldwide business activities. The Company believes that results by geographic region or client sector are not necessarily meaningful in understanding its business. For the years ended December 31, 2017, 2016 and 2015, the U.K. was the only individual foreign country in which the Company had a subsidiary that accounted for 10% or more of the total revenues or total long-lived assets. Revenues and long-lived assets are attributed to geographic area based on the location of the particular subsidiary. Long-lived assets are defined as furniture, equipment, leasehold improvements and capitalized software Year Ended December 31, 2017 2016 2015 (In thousands) Revenues United States $ 336,867 $ 314,343 $ 262,558 United Kingdom 59,151 54,015 39,338 Other 1,453 1,561 1,202 Total $ 397,471 $ 369,919 $ 303,098 As of December 31, 2017 2016 (In thousands) Long-lived assets, as defined United States $ 27,990 $ 23,370 United Kingdom 10,532 7,713 Other 26 21 Total $ 38,548 $ 31,104

Retirement and Deferred Compens

Retirement and Deferred Compensation Plans	12 Months Ended
	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Retirement and Deferred Compensation Plans	14. Retirement and Deferred Compensation Plans The Company, through its U.S. and U.K. subsidiaries, offers its employees the opportunity to invest in defined contribution plans. For the years ended December 31, 2017, 2016 and 2015, the Company contributed $1.8 million, $1.9 million and $1.9 million, respectively, to the plans. The Company offers a non-qualified deferred cash incentive plan to certain officers and other employees. Under the plan, eligible employees may defer up to 100% of their annual cash incentive pay. The Company has elected to fund its deferred compensation obligations through a rabbi trust. The rabbi trust is subject to creditor claims in the event of insolvency but such assets are not available for general corporate purposes. Assets held in the rabbi trust are invested in mutual funds, as selected by the participants, which are designated as trading securities and carried at fair value. As of December 31, 2017 and 2016, the fair value of the mutual fund investments and deferred compensation obligations were $3.2 and $1.3 million, respectively. Changes in the fair value of securities held in the rabbi trust are recognized as trading gains and losses and included in other revenues and offsetting increases or decreases in the deferred compensation obligation are recorded in employee compensation and benefits. For the years ended December 31, 2017 and 2016, the trading gains and compensation expense were $0.4 and $0.2 million, respectively. There were no trading gains or compensation expense for the year ended December 31, 2015 as the initial deferrals occurred in January 2016.

Customer Concentration

Customer Concentration	12 Months Ended
	Dec. 31, 2017
Risks And Uncertainties [Abstract]
Customer Concentration	15. Customer Concentration During the years ended December 31, 2017, 2016 and 2015, no single client accounted for more than 10% of total revenue. One institutional investor client accounted for approximately 12.2%, 14.2% and 15.3% of trading volumes during the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, investment funds managed by this institutional investor client beneficially owned approximately 8.3% of the outstanding shares of the Company’s common stock, primarily through passive index and ETF funds.

Significant Accounting Polici24

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
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.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents includes cash and money market instruments that are primarily maintained at one major global bank. Given this concentration, the Company is exposed to certain credit risk in relation to its deposits at this bank. The Company defines cash equivalents as short-term interest-bearing investments with maturities at the time of purchase of three months or less.
Investments	Investments The Company determines the appropriate classification of securities at the time of purchase which are recorded in the Consolidated Statements of Financial Condition on the trade date. Securities are classified as available-for-sale or trading. The Company’s available-for-sale investments are comprised of municipal bonds and investment grade corporate debt securities. Available-for-sale investments are carried at fair value with the unrealized gains or losses reported in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Trading investments primarily include investment grade corporate debt securities and are carried at fair value, with realized and unrealized gains or losses included in other income in the Consolidated Statements of Operations. The Company assesses whether an other-than-temporary impairment loss on the available-for-sale investments has occurred due to declines in fair value or other market conditions. The portion of an other-than-temporary impairment related to credit loss is recorded as a charge in the Consolidated Statements of Operations. The remainder is recognized in accumulated other comprehensive loss if the Company does not intend to sell the security and it is more likely than not that the Company will not be required to sell the security prior to recovery. No charges for other-than-temporary losses were recorded during the years ended December 31, 2017, 2016 and 2015.
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.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts 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 doubtful accounts is based upon the historical collection experience and specific collection issues that have been identified. Additions to the allowance for doubtful accounts are charged to bad debt expense, which is included in general and administrative expense in the Company’s Consolidated Statements of Operations. The allowance for doubtful accounts was $0.2 million, $0.1 million and $0.1 million as of December 31, 2017, 2016 and 2015, respectively. The provision for bad debts was $0.4 million, $0.2 million and $0.2 million for the years ended December 31, 2017, 2016 and 2015, respectively. Write-offs and other charges against the allowance for doubtful accounts were $0.1 million for each year ended December 31, 2017, 2016 and 2015, respectively.
Depreciation and Amortization	Depreciation and Amortization Fixed assets are carried at cost less accumulated depreciation. The Company uses the straight-line method of depreciation over three to seven years. The Company amortizes leasehold improvements on a straight-line basis over the lesser of the life of the improvement or the remaining term of the lease.
Software Development Costs	Software Development Costs The Company capitalizes certain costs associated with the development of internal use software, including among other items, employee compensation and related benefits and third party consulting costs at the point at which the conceptual formulation, design and testing of possible software project alternatives have been completed. Once the product is ready for its intended use, such costs are amortized on a straight-line basis over three years. The Company reviews the amounts capitalized for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable.
Cash Provided as Collateral	Cash Provided as Collateral Cash is provided as collateral for broker-dealer clearing accounts. Cash provided as collateral is included in prepaid expenses and other assets in the Consolidated Statements of Financial Condition.
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 general and administrative expense 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 majority of the Company’s revenues are derived from commissions for trades executed on its platform and distribution fees that are billed to its broker-dealer clients on a monthly basis. The Company also derives revenues from information and post-trade services, technology products and services, investment income and other income. Commission revenue. Commissions are generally calculated as a percentage of the notional dollar volume of bonds traded on the platform and vary based on the type, size, yield and maturity of the bond traded. Under the Company’s transaction fee plans, bonds that are more actively traded or that have shorter maturities are generally charged lower commissions, while bonds that are less actively traded or that have longer maturities generally command higher commissions. For 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 the commission through the difference in price between the two matched principal trades. Fee programs for certain products include distribution fees which are recognized monthly. Information Services. The Company generates revenue from data licensed to its broker-dealer clients, institutional investor clients and data-only subscribers, professional consulting services, technology software licenses and maintenance and support services. Information service revenues are invoiced monthly, quarterly or annually. When billed in advance, information service revenues are deferred and recognized monthly on a straight-line basis. Revenue from professional consulting services are recognized as services are performed and software license subscription revenue and maintenance and support services are recognized ratably over the contract period. Post-trade Services . The Company generates revenue from regulatory transaction reporting, trade publication and trade matching services. Revenue is recognized in the period the services are provided.
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. Effective upon the Company’s adoption of ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting” (“ASU 2016-09”) on January 1, 2017, the Company accounts for forfeitures as they occur. Prior to the adoption of ASU 2016-09, expected forfeitures were included in determining share-based compensation expense.
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 general and administrative expenses in the Consolidated Statements of Operations. Effective upon the Company’s adoption of ASU 2016-09 all tax effects related to share-based payments are recorded through tax expense in the periods during which the awards are exercised or vest. On December 22, 2017, the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (“SAB 118”) to address the application of U.S. generally accepted accounting principles (“GAAP”) related to the enactment of the Tax Cuts and Jobs Act (the “Tax Act”). SAB 118 allows the Company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The measurement period ends when the Company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. The Company expects to complete its analysis within the measurement period in accordance with SAB 118.
Business Combinations, Goodwill and Intangible Assets	Business Combinations, Goodwill and Intangible Assets Business combinations are accounted for under the purchase method of accounting. The total cost of an acquisition is allocated to the underlying net assets based on their respective estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. Determining the fair value of certain assets acquired and liabilities assumed is judgmental in nature and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash flows, discount rates, growth rates and asset lives. The Company operates as a single reporting unit. Subsequent to 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 on a straight-line basis over their estimated useful lives, ranging from three to 15 years. 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.
Out-of-Period Adjustments	Out-of-Period Adjustments During the first quarter of 2016, the Company determined that it had incorrectly recorded deferred taxes for the cumulative translation adjustment (“CTA”) that arises from converting the local currency financial statements into U.S. dollars. Upon making a permanent reinvestment assertion on unremitted earnings from foreign subsidiaries effective January 1, 2013, the Company should have eliminated any deferred tax balances derived from the CTA balance. The Company also determined that gains and losses on the foreign currency forward contracts used to hedge the net investment in certain foreign subsidiaries were not appropriately considered as taxable income or expense in the consolidated tax returns. The Company assessed these errors and determined that they were not material to previous reporting periods. Therefore, the Company recorded these items as out-of-period adjustments in the three months ended March 31, 2016 by decreasing deferred tax assets by $3.1 million, decreasing other comprehensive income by $2.1 million and increasing prepaid expenses and other assets by $1.0 million in the Consolidated Statements of Financial Condition.
Reclassifications	Reclassifications Certain reclassifications have been made to the prior years’ Consolidated Financial Statements in order to conform to the current year presentation. The Company reclassified certain revenue line items on the consolidated statements of operations to separately reflect information service revenues and post-trade service revenues. Such reclassifications had no effect on previously reported net income.
Accounting Pronouncements, Recently Adopted	Accounting Pronouncements, Recently Adopted Effective January 1, 2017, the Company adopted ASU 2016-09 which simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, statutory tax withholding requirements and classification on the statement of cash flows. Beginning January 1, 2017, the tax effects related to share-based payments are recorded through the income tax provision and the Company has elected to account for forfeitures as they occur. The adoption of ASU 2016-09 will cause volatility in the Company’s net income, effective tax rate and diluted earnings per share. The volatility in future periods will depend on the Company’s stock price at the vesting date for restricted stock awards or exercise date for stock options and the number of awards that vest or are exercised in each period. Under the new guidance, excess tax benefits from share-based compensation are included as an operating activity in the Company’s Consolidated Statements of Cash Flows. Prior period cash flows have been adjusted to conform to the new presentation.
Accounting Pronouncements, Not Yet Adopted as of December 31, 2017	Accounting Pronouncements, Not Yet Adopted as of December 31, 2017 In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”) requiring an entity to recognize revenue for the transfer of goods or services equal to the amount that it expects to be entitled to receive for those goods or services. The standard also requires new disclosure concerning contracts with customers, including the significant judgments made when applying the guidance. The Company adopted ASU 2014-09 effective January 1, 2018 using the modified retrospective transition approach. The Company completed its analysis and the adoption of this guidance will not have a material impact on the Company’s Consolidated Financial Statements. In February 2016, the FASB issued ASU 2016-02, “Leases” (“ASU 2016-02”) requiring lessees to recognize lease assets and lease liabilities on the balance sheet for those leases previously classified as operating leases. ASU 2016-02 will be effective for the Company beginning January 1, 2019 and early adoption is permitted and should be applied prospectively. The Company is currently evaluating the potential adoption impact and expects to recognize lease assets and lease liabilities in its Consolidated Statements of Financial Condition. The Company does not expect material changes to the recognition of operating lease expense in its Consolidated Statements of Operations. In January 2017, the FASB issued ASU 2017-04, “Intangibles-Goodwill and Other” (“ASU 2017-04”). ASU 2017-04 simplifies the testing for goodwill impairment. The guidance will be effective for the Company beginning January 1, 2020 and early adoption is permitted and should be applied prospectively. The adoption of this guidance is not expected to have a material effect on the Company’s Consolidated Financial Statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Valuation of Company's Assets and Liabilities Measured at Fair Value	The following table summarizes the valuation of the Company’s assets and liabilities measured at fair value as categorized based on the hierarchy described in Note 2. Level 1 Level 2 Level 3 Total (In thousands) As of December 31, 2017 Money market funds $ 88,562 $ — $ — $ 88,562 Securities available-for-sale Corporate debt — 145,052 — 145,052 Trading securities Corporate debt — 91,302 — 91,302 Mutual funds held in rabbi trust — 3,167 — 3,167 Foreign currency forward position — (702 ) — (702 ) Total $ 88,562 $ 238,819 $ — $ 327,381 As of December 31, 2016 Money market funds $ 58,573 $ — $ — $ 58,573 Securities available-for-sale Corporate debt — 118,870 — 118,870 Trading securities Corporate debt — 74,207 — 74,207 Mutual funds held in rabbi trust — 1,327 — 1,327 Foreign currency forward position — (266 ) — (266 ) Total $ 58,573 $ 194,138 $ — $ 252,711
Summary of Foreign Currency Forward Contracts	A summary of the foreign currency forward position is as follows: As of December 31, 2017 2016 (In thousands) Notional value $ 84,422 $ 66,972 Fair value of notional 85,124 67,238 Fair value of the (liability) $ (702 ) $ (266 )
Summary of Company's Investments	The following is a summary of the Company’s investments: Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value (In thousands) As of December 31, 2017 Securities available-for-sale Corporate debt $ 145,526 $ 9 $ (483 ) $ 145,052 Trading securities Corporate debt 91,578 30 (306 ) 91,302 Mutual funds held in rabbi trust 2,729 438 — 3,167 Total trading securities 94,307 468 (306 ) 94,469 Total investments $ 239,833 $ 477 $ (789 ) $ 239,521 As of December 31, 2016 Securities available-for-sale Corporate debt $ 119,073 $ 13 $ (216 ) $ 118,870 Trading securities Corporate debt 74,394 47 (234 ) 74,207 Mutual funds held in rabbi trust 1,212 115 — 1,327 Total trading securities 75,606 162 (234 ) 75,534 Total investments $ 194,679 $ 175 $ (450 ) $ 194,404
Summary of Fair Value of Investments Based upon Contractual Maturities	The following table summarizes the fair value of the investments based upon the contractual maturities: As of December 31, 2017 2016 (In thousands) Less than one year $ 130,738 $ 117,904 Due in 1 - 5 years 108,783 76,500 Total $ 239,521 $ 194,404
Fair Values and Unrealized Losses on Investments	The following table provides fair values and unrealized losses on investments and by the aging of the securities' continuous unrealized loss position as of December 31, 2017 and 2016 respectively: Less than Twelve Months Twelve Months or More Total Estimated fair value Gross unrealized losses Estimated fair value Gross unrealized losses Estimated fair value Gross unrealized losses (In thousands) As of December 31, 2017 Corporate debt $ 177,114 $ (536 ) $ 26,476 $ (253 ) $ 203,590 $ (789 ) As of December 31, 2016 Corporate debt $ 136,667 $ (449 ) $ 2,000 $ (1 ) $ 138,667 $ (450 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Company's Intangible Assets	Goodwill and intangible assets with indefinite lives was $59.7 million as of both December 31, 2017 and 2016. Intangible assets that are subject to amortization, including the related accumulated amortization, are comprised of the following: December 31, 2017 December 31, 2016 Cost Accumulated amortization Net carrying amount Cost Accumulated amortization Net carrying amount (In thousands) Technology $ 5,770 $ (5,770 ) $ — $ 5,770 $ (5,770 ) $ — Customer relationships 5,647 (2,301 ) 3,346 5,628 (1,897 ) 3,731 Non-competition agreements 380 (380 ) — 380 (380 ) — Tradenames 370 (370 ) — 370 (370 ) — Total $ 12,167 $ (8,821 ) $ 3,346 $ 12,148 $ (8,417 ) $ 3,731

Capitalized Software, Furnitu27

Capitalized Software, Furniture, Equipment and Leasehold Improvements (Tables)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Capitalized Software Development Costs, Furniture, Equipment and Leasehold Improvements, Net of Accumulated Depreciation and Amortization	Capitalized software development costs, furniture, equipment and leasehold improvements, net of accumulated depreciation and amortization, are comprised of the following: As of December 31, 2017 2016 (In thousands) Software development costs $ 86,129 $ 71,551 Computer hardware and related software 35,945 20,152 Office hardware 4,575 4,228 Furniture and fixtures 2,347 2,001 Leasehold improvements 11,016 8,351 140,012 106,283 Accumulated depreciation and amortization (101,464 ) (75,179 ) Total $ 38,548 $ 31,104

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Provision for Income Taxes	The provision for income taxes consists of the following: Year Ended December 31, 2017 2016 2015 (In thousands) Current: Federal $ 36,045 $ 45,455 $ 38,357 State and local 3,848 7,087 7,180 Foreign 7,234 6,166 4,346 Total current provision 47,127 58,708 49,883 Deferred: Federal 6,171 5,884 1,492 State and local 661 1,141 299 Foreign (280 ) (303 ) 189 Total deferred provision 6,552 6,722 1,980 Provision for income taxes $ 53,679 $ 65,430 $ 51,863
Difference Between the Company's Reported Provision for Income Taxes and the U.S. Federal Statutory Rate	The difference between the Company’s reported provision for income taxes and the U.S. federal statutory rate of 35% is as follows: Year Ended December 31, 2017 2016 2015 U.S. federal tax at statutory rate 35.0 % 35.0 % 35.0 % State and local taxes - net of federal benefit 1.5 2.9 3.4 Credits and deductions related to research activities (1.2 ) (1.3 ) (1.3 ) Foreign rate differential benefit (2.9 ) (2.3 ) (2.0 ) Excess tax benefit from stock-based compensation (11.6 ) — — Tax Cuts and Jobs Act provisional tax charge 5.8 — — Other, net — (0.2 ) — Provision for income taxes 26.6 % 34.1 % 35.1 %
Summary of Company's Net Deferred Tax Assets	The following is a summary of the Company’s net deferred tax assets: As of December 31, 2017 2016 (In thousands) Deferred tax assets: U.S. net operating loss carryforwards $ 872 $ 1,909 Capital loss carryforwards 4,648 7,235 Stock compensation expense 4,534 11,307 Other 1,143 1,468 Total deferred tax assets 11,197 21,919 Valuation allowance (4,648 ) (7,235 ) Net deferred tax assets 6,549 14,684 Deferred tax liabilities: Depreciation and amortization (1,369 ) (1,456 ) Capitalized software development costs (3,479 ) (4,923 ) Intangible assets (967 ) (1,037 ) Deferred tax assets, net $ 734 $ 7,268
Summary of Changes in Valuation Allowance	A summary of the changes in the valuation allowance is as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Valuation allowance at beginning of year $ 7,235 $ 7,294 $ 7,428 (Decrease) to valuation allowance attributable to: Federal and state tax rate changes (2,587 ) (59 ) (134 ) Valuation allowance at end of year $ 4,648 $ 7,235 $ 7,294
Reconciliation of the Unrecognized Tax Benefits	A reconciliation of the unrecognized tax benefits is as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Balance at beginning of year $ 29 $ 265 $ 265 Additions attributable to state and local apportionment 2,650 — — Reductions for tax positions of prior years (29 ) (236 ) — Balance at end of year $ 2,650 $ 29 $ 265

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of the Change in the Company's Outstanding Shares of Common Stock	The following is a summary of the change in the Company’s outstanding shares of voting common stock: Year Ended December 31, 2017 2016 2015 (In thousands) Outstanding shares of voting common stock at the beginning of year 37,544 37,409 37,319 Exercise of stock options 262 181 183 Issuance of restricted stock, net of shares withheld for withholding tax payments and cancellations 39 104 178 Repurchases (224 ) (150 ) (271 ) Outstanding shares of voting common stock at the end of year 37,621 37,544 37,409

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense	Total stock-based compensation expense was as follows: Year Ended December 31, 2017 2016 2015 (In thousands) Employees: Restricted stock and performance shares $ 11,566 $ 12,459 $ 10,792 Stock options 1,882 1,143 826 13,448 13,602 11,618 Non-employee directors: Restricted stock 973 909 901 Total stock-based compensation $ 14,421 $ 14,511 $ 12,519
Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted	The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted for the three years ended December 31, 2017: 2017 2016 2015 Expected life (years) 5.0 6.0 7.0 Risk-free interest rate 1.9 % 1.9 % 1.9 % Expected volatility 28.0 % 33.0 % 56.7 % Expected dividend yield 0.8 % 1.0 % 1.1 %
Stock Option Activity	The following table reports stock option activity during the three years ended December 31, 2017 and the intrinsic value as of December 31, 2017: Number of Shares Weighted-Average Exercise Price ($) Remaining Contractual Term Intrinsic Value ($) (In thousands) Outstanding at December 31, 2014 1,014,420 $ 13.81 Granted 120,650 88.15 Canceled — — Exercised (196,034 ) 11.60 Outstanding at December 31, 2015 939,036 23.83 Granted 112,988 102.40 Canceled (874 ) 101.77 Exercised (195,410 ) 12.35 Outstanding at December 31, 2016 855,740 36.80 Granted 54,838 156.85 Canceled — — Exercised (380,967 ) 11.26 $ 68,068 Outstanding at December 31, 2017 529,611 67.60 3.3 71,046 Exercisable at December 31, 2017 254,079 24.61 3.0 45,009
Summary of Performance of Share Activity for Annual Awards	The following table reports performance share activity for annual awards for the three years ended December 31, 2017: Performance year: 2017 2016 2015 Share pay-out plan 12,971 15,390 28,520 Actual share pay-out in following year 8,094 21,423 37,696 Weighted average fair value per share on grant date $ 155.53 $ 101.77 $ 70.60
Restricted Stock and Performance Share Activity	The following table reports restricted stock and performance share activity during the three years ended December 31, 2017: Number of Restricted Shares Weighted-Average Grant Date Fair Value Outstanding at December 31, 2014 435,989 $ 41.83 Granted 117,668 Performance share pay-out 117,647 Canceled (3,845 ) Vested (235,321 ) Outstanding at December 31, 2015 432,138 $ 56.24 Granted 95,419 Performance share pay-out 61,936 Canceled (12,786 ) Vested (192,729 ) Outstanding at December 31, 2016 383,978 $ 71.50 Granted 61,434 Performance share pay-out 21,422 Canceled (4,590 ) Vested (142,645 ) Outstanding at December 31, 2017 319,599 $ 88.77

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Common Share	The following table sets forth the computation of basic and diluted earnings per common share: Year Ended December 31, 2017 2016 2015 (In thousands, except per share amounts) Net income $ 148,089 $ 126,172 $ 96,037 Basic weighted average shares outstanding 36,864 36,844 36,690 Dilutive effect of stock options and restricted stock 1,174 894 947 Diluted weighted average shares outstanding 38,038 37,738 37,637 Basic earnings per share $ 4.02 $ 3.42 $ 2.62 Diluted earnings per share $ 3.89 $ 3.34 $ 2.55

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Summary of Minimum Rental Commitments under Operating Leases	Minimum rental commitments as of December 31, 2017 under such operating leases were as follows (in thousands): 2018 $ 5,000 2019 9,659 2020 10,770 2021 10,149 2022 9,129 2023 and thereafter 99,166 $ 143,873

Segment and Geographic Inform33

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Summary of Revenue and Long-lived Assets	Information regarding revenue for the three years ended December 31, 2017, 2016 and 2015 and long-lived assets as of December 31, 2017 and 2016 follows: Year Ended December 31, 2017 2016 2015 (In thousands) Revenues United States $ 336,867 $ 314,343 $ 262,558 United Kingdom 59,151 54,015 39,338 Other 1,453 1,561 1,202 Total $ 397,471 $ 369,919 $ 303,098 As of December 31, 2017 2016 (In thousands) Long-lived assets, as defined United States $ 27,990 $ 23,370 United Kingdom 10,532 7,713 Other 26 21 Total $ 38,548 $ 31,104

Organization and Principal Bu34

Organization and Principal Business Activity - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Institutional_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	1,300

Significant Accounting Polici35

Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2016
Significant Accounting Policies [Line Items]
Maximum maturity period for classification of investments as cash equivalents	3 months
Investments other-than-temporary losses	$ 0	$ 0	$ 0
Allowance for doubtful accounts	178,000	82,000	100,000
Provision for bad debts	400,000	200,000	200,000
Write-offs and other charges against the allowance for doubtful accounts	100,000	100,000	$ 100,000
Deferred tax assets, net	1,737,000	8,562,000
Other comprehensive income	(10,226,000)	(12,228,000)
Prepaid expenses and other assets	$ 18,717,000	$ 11,618,000
Restatement Adjustment [Member]
Significant Accounting Policies [Line Items]
Deferred tax assets, net				$ 3,100,000
Other comprehensive income				2,100,000
Prepaid expenses and other assets				$ 1,000,000
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	3 years
Minimum [Member] | Internally Developed Software [Member]
Significant Accounting Policies [Line Items]
Estimated life of intangible assets	3 years

Net Capital Requirements - Addi

Net Capital Requirements - Additional Information (Detail) $ in Millions	Dec. 31, 2017USD ($)
Brokers And Dealers [Abstract]
Aggregate net capital and financial resources in excess of required level	$ 130.5
Aggregate net capital and financial resources, minimum capital requirement	$ 14.8

Fair Value Measurements - Valua

Fair Value Measurements - Valuation of Company's Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	$ 88,562	$ 58,573
Trading securities	94,469	75,534
Assets Fair Value Total	327,381	252,711
Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	145,052	118,870
Trading securities	91,302	74,207
Mutual Funds Held In Rabbi Trust [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading securities	3,167	1,327
Foreign Currency Forward Position [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Foreign currency forward position	(702)	(266)
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds	88,562	58,573
Assets Fair Value Total	88,562	58,573
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Fair Value Total	238,819	194,138
Level 2 [Member] | Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities available-for-sale	145,052	118,870
Trading securities	91,302	74,207
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	3,167	1,327
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	$ (702)	$ (266)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Hedge derivative expiration period	1 month
Proceeds from the sales and maturities of securities available-for-sale	$ 219.2	$ 69.5	$ 35.2
Net unrealized losses on corporate debt trading securities	$ 0.1	$ 0.2

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Foreign Currency Forward Contracts (Detail) - Foreign Currency Forward Position [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives Fair Value [Line Items]
Notional value	$ 84,422	$ 66,972
Fair value of notional	85,124	67,238
Fair value of the (liability)	$ (702)	$ (266)

Fair Value Measurements - Sum40

Fair Value Measurements - Summary of Company's Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	$ 94,307	$ 75,606
Trading securities, Gross unrealized gains	468	162
Trading securities, Gross unrealized losses	(306)	(234)
Trading securities, Estimated fair value	94,469	75,534
Investments, Amortized cost	239,833	194,679
Investments, Gross unrealized gains	477	175
Investments, Gross unrealized losses	(789)	(450)
Investments, Estimated fair value	239,521	194,404
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Securities available-for-sale, Amortized cost	145,526	119,073
Securities available-for-sale, Gross unrealized gains	9	13
Securities available-for-sale, Gross unrealized losses	(483)	(216)
Securities available-for-sale, Estimated fair value	145,052	118,870
Trading securities, Amortized cost	91,578	74,394
Trading securities, Gross unrealized gains	30	47
Trading securities, Gross unrealized losses	(306)	(234)
Trading securities, Estimated fair value	91,302	74,207
Mutual Funds Held In Rabbi Trust [Member]
Schedule Of Available For Sale Securities [Line Items]
Trading securities, Amortized cost	2,729	1,212
Trading securities, Gross unrealized gains	438	115
Trading securities, Estimated fair value	$ 3,167	$ 1,327

Fair Value Measurements - Sum41

Fair Value Measurements - Summary of Fair Value of Investments Based upon Contractual Maturities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Less than one year	$ 130,738	$ 117,904
Due in 1 - 5 years	108,783	76,500
Total	$ 239,521	$ 194,404

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values and Unrealized Losses on Investments (Detail) - Corporate Debt [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Less than Twelve Months, Estimated fair value	$ 177,114	$ 136,667
Less than Twelve Months, Gross unrealized losses	(536)	(449)
Twelve Months or More, Estimated fair value	26,476	2,000
Twelve Months or More, Gross unrealized losses	(253)	(1)
Estimated fair value, Total	203,590	138,667
Gross unrealized losses, Total	$ (789)	$ (450)

Goodwill and Intangible Asset43

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 63,059	$ 63,443
Amortization expense associated with identifiable intangible assets	400	700	$ 2,300
Estimated total amortization expense 2018	400
Estimated total amortization expense 2019	400
Estimated total amortization expense 2020	400
Estimated total amortization expense 2021	400
Estimated total amortization expense 2022	400
Indefinite-lived Intangible Assets [Member]
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	$ 59,700	$ 59,700

Goodwill and Intangible Asset44

Goodwill and Intangible Assets - Summary of Company's Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Cost	$ 12,167	$ 12,148
Accumulated amortization	(8,821)	(8,417)
Net carrying amount	3,346	3,731
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Cost	5,770	5,770
Accumulated amortization	(5,770)	(5,770)
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Cost	5,647	5,628
Accumulated amortization	(2,301)	(1,897)
Net carrying amount	3,346	3,731
Non-Competition Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Cost	380	380
Accumulated amortization	(380)	(380)
Tradenames - Finite Life [Member]
Finite Lived Intangible Assets [Line Items]
Cost	370	370
Accumulated amortization	$ (370)	$ (370)

Capitalized Software, Furnitu45

Capitalized Software, Furniture, Equipment and Leasehold Improvements - Capitalized Software Development Costs, Furniture, Equipment and Leasehold Improvements, Net of Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 140,012	$ 106,283
Accumulated depreciation and amortization	(101,464)	(75,179)
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	38,548	31,104
Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	86,129	71,551
Computer Hardware and Related Software [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	35,945	20,152
Office Hardware [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	4,575	4,228
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	2,347	2,001
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Furniture, equipment, leasehold improvements and capitalized software, Gross	$ 11,016	$ 8,351

Capitalized Software, Furnitu46

Capitalized Software, Furniture, Equipment and Leasehold Improvements - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Software development costs	$ 13.9	$ 12.3

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 36,045	$ 45,455	$ 38,357
State and local	3,848	7,087	7,180
Foreign	7,234	6,166	4,346
Total current provision	47,127	58,708	49,883
Deferred:
Federal	6,171	5,884	1,492
State and local	661	1,141	299
Foreign	(280)	(303)	189
Total deferred provision	6,552	6,722	1,980
Provision for income taxes	$ 53,679	$ 65,430	$ 51,863

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Pre Tax Income [Line Items]
Pre-tax income from U.S. operations		$ 165.2	$ 161.9	$ 126.4
U.S. federal tax at statutory rate		35.00%	35.00%	35.00%
Provisional tax charge recorded due to enactment of Tax Act		$ 11.7
Re-measurement of U.S. deferred tax assets		6.7
Repatriation taxes on accumulated undistributed foreign earnings		$ 5
Additional annual limitations		50% or greater change
Percentage of change in ownership		50.00%
Additional annual limitations period		3 years
Capital loss on the sale		$ 20.6
Capital loss carried back		$ 1.2
New York State [Member] | Earliest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination		2,010
New York State [Member] | Latest Tax Year [Member]
Schedule Of Pre Tax Income [Line Items]
Income tax year under examination		2,013
Scenario Forecast [Member]
Schedule Of Pre Tax Income [Line Items]
U.S. federal tax at statutory rate	21.00%
Foreign Country [Member]
Schedule Of Pre Tax Income [Line Items]
Pre-tax income from foreign operations		$ 36.6	$ 29.7	$ 21.5
US Country [Member]
Schedule Of Pre Tax Income [Line Items]
Net operating loss carryforwards related to prior ownership change		$ 4.2
Net operating loss carryforwards, expiration date		2,021

Income Taxes - Difference Betwe

Income Taxes - Difference Between the Company's Reported Provision for Income Taxes and the U.S. Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. federal tax at statutory rate	35.00%	35.00%	35.00%
State and local taxes - net of federal benefit	1.50%	2.90%	3.40%
Credits and deductions related to research activities	(1.20%)	(1.30%)	(1.30%)
Foreign rate differential benefit	(2.90%)	(2.30%)	(2.00%)
Excess tax benefit from stock-based compensation	(11.60%)
Tax Cuts and Jobs Act provisional tax charge	5.80%
Other, net		(0.20%)
Provision for income taxes	26.60%	34.10%	35.10%

Income Taxes - Summary of Compa

Income Taxes - Summary of Company's Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Capital loss carryforwards	$ 4,648	$ 7,235
Stock compensation expense	4,534	11,307
Other	1,143	1,468
Total deferred tax assets	11,197	21,919
Valuation allowance	(4,648)	(7,235)	$ (7,294)	$ (7,428)
Net deferred tax assets	6,549	14,684
Deferred tax liabilities:
Depreciation and amortization	(1,369)	(1,456)
Capitalized software development costs	(3,479)	(4,923)
Intangible assets	(967)	(1,037)
Deferred tax assets, net	734	7,268
US Country [Member]
Deferred tax assets:
U.S. net operating loss carryforwards	$ 872	$ 1,909

Income Taxes - Summary of Chang

Income Taxes - Summary of Changes in Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Valuation allowance at beginning of year	$ 7,235	$ 7,294	$ 7,428
Federal and state tax rate changes	(2,587)	(59)	(134)
Valuation allowance at end of year	$ 4,648	$ 7,235	$ 7,294

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 29	$ 265	$ 265
Additions attributable to state and local apportionment	2,650
Reductions for tax positions of prior years	(29)	(236)	0
Balance at end of year	$ 2,650	$ 29	$ 265

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended												12 Months Ended
	Sep. 30, 2017	Jan. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 31, 2016
Class of Stock [Line Items]
Common stock, shares authorized			110,000,000				110,000,000								110,000,000	110,000,000
Common stock entitles															One
Cash dividends declared per common share			$ 0.33	$ 0.33	$ 0.33	$ 0.33	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 1.32	$ 1.04	$ 0.80
Share Repurchase Program [Member]
Class of Stock [Line Items]
Shares repurchase program period	15 months	2 years
Shares repurchase program authorized	$ 100,000,000	$ 25,000,000		$ 100,000,000
Shares repurchase program additional authorized amount																		$ 50,000,000
Commencement date	2017-10
Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized			10,000,000				10,000,000								10,000,000	10,000,000
Common Stock Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized			110,000,000				110,000,000								110,000,000	110,000,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of the Companys Change in the Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,543,775
Exercise of stock options	380,967	195,410	196,034
Outstanding shares of voting common stock at the end of year	37,620,736	37,543,775
Voting Common Stock [Member]
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,544,000	37,409,000	37,319,000
Exercise of stock options	262,000	181,000	183,000
Issuance of restricted stock, net of shares withheld for withholding tax payments and cancellations	39,000	104,000	178,000
Repurchases	(224,000)	(150,000)	(271,000)
Outstanding shares of voting common stock at the end of year	37,621,000	37,544,000	37,409,000

Stock-Based Compensation Plan55

Stock-Based Compensation Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Apr. 01, 2017	Jan. 31, 2016	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant under the stock incentive plans				219,983
Exercise price for the shares of the Company's common stock				$ 40.08	$ 32.24	$ 36.46
Grant date fair value				$ 68,068
Fair value assumptions, Dividend yield rate				0.80%	1.00%	1.10%
Closing price of common stock				$ 201.75
Unrecognized compensation costs related to non-vested				$ 4,300
Weighted-average period over which cost is expected to be recognized				2 years 2 months 12 days
Pay-out ranges, Minimum				0.00%
Pay-out ranges, Maximum				150.00%
Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs related to non-vested				$ 18,600
Weighted-average period over which cost is expected to be recognized				1 year 8 months 12 days
Employees Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants						1 year
Number of non-option equity instruments granted during the period				1,034	1,190	0
Percentage of shares grant to participants						20.00%
Chief Executive Officer [Member] | Incentive Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Expiration Period			5 years 6 months
Exercise price for the shares of the Company's common stock			$ 88.25
Number of stock option equity instruments granted during the period			119,981
Grant date fair value			$ 2,000
Percentage of fair market value of the common stock on the grant date			125.00%
Fair value assumptions, Risk free interest rate			1.40%
Fair value assumptions, Volatility rate			27.30%
Fair value assumptions, Dividend yield rate			0.90%
Chief Executive Officer [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value			$ 6,000
Fair value assumptions, Risk free interest rate			1.30%
Fair value assumptions, Volatility rate			27.30%
Fair value assumptions, Dividend yield rate			0.90%
Number of non-option equity instruments granted during the period			116,659
Share-based compensation arrangement by share-based payment award, equity instruments other than options, nonvested, number					24,240	92,419
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award award vesting date			Jan. 15, 2018
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche One [Member] | Incentive Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights			33.33%
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights			50.00%
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Two [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights			50.00%
Share-based compensation arrangement by share-based payment award award vesting date			Jan. 15, 2019
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Two [Member] | Incentive Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights			33.33%
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Three [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award award vesting date			Jan. 15, 2020
Chief Executive Officer [Member] | Share-based Compensation Award, Tranche Three [Member] | Incentive Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights			33.33%
Officers and Senior Managers [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Expiration Period	2 years	3 years
Pay-out ranges, Minimum	0.00%	0.00%
Pay-out ranges, Maximum	150.00%	150.00%
Number of non-option equity instruments granted during the period	9,367	33,509
Fair value per share on the grant date	$ 186.74	$ 103.30
Officers and Senior Managers [Member] | Share-based Compensation Award, Tranche One [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights	50.00%	50.00%
Share-based compensation arrangement by share-based payment award award vesting date	Apr. 1, 2020	Jan. 31, 2020
Officers and Senior Managers [Member] | Share-based Compensation Award, Tranche Two [Member] | Performance Based Share [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights	50.00%	50.00%
Share-based compensation arrangement by share-based payment award award vesting date	Apr. 1, 2021	Jan. 31, 2021
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				3 years
Options Expiration Period				6 years
Minimum [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				3 years
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				5 years
Options Expiration Period				10 years
Maximum [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Period vested for option grants				5 years

Stock-Based Compensation Plan56

Stock-Based Compensation Plans - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 13,448	$ 13,602	$ 11,618
Employees [Member] | Restricted Stock and Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	11,566	12,459	10,792
Employees [Member] | Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	1,882	1,143	826
Non-Employee Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	14,421	14,511	12,519
Non-Employee Directors [Member] | Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 973	$ 909	$ 901

Stock-Based Compensation Plan57

Stock-Based Compensation Plans - Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected life (years)	5 years	6 years	7 years
Risk-free interest rate	1.90%	1.90%	1.90%
Expected volatility	28.00%	33.00%	56.70%
Expected dividend yield	0.80%	1.00%	1.10%

Stock-Based Compensation Plan58

Stock-Based Compensation Plans - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	855,740	939,036	1,014,420
Number of Shares, Granted	54,838	112,988	120,650
Number of Shares, Canceled		(874)
Number of Shares, Exercised	(380,967)	(195,410)	(196,034)
Number of Shares, Ending Balance	529,611	855,740	939,036
Number of Shares, Exercisable	254,079
Weighted Average Exercise Price, Beginning Balance	$ 36.80	$ 23.83	$ 13.81
Weighted Average Exercise Price, Granted	156.85	102.40	88.15
Weighted Average Exercise Price, Canceled		101.77
Weighted Average Exercise Price, Exercised	11.26	12.35	11.60
Weighted Average Exercise Price, Ending Balance	67.60	$ 36.80	$ 23.83
Weighted Average Exercise Price, Exercisable	$ 24.61
Remaining Contractual Term, Outstanding at December 31, 2016	3 years 3 months 18 days
Remaining Contractual Term, Exercisable at December 31, 2016	3 years
Intrinsic Value, Exercised	$ 68,068
Intrinsic Value, Ending Balance	71,046
Intrinsic Value, Exercisable	$ 45,009

Stock-Based Compensation Plan59

Stock-Based Compensation Plans - Summary of Performance of Share Activity for Annual Awards (Detail) - Performance Shares [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share pay-out plan	12,971	15,390	28,520
Actual share pay-out in following year	8,094	21,423	37,696
Weighted average fair value per share on grant date	$ 155.53	$ 101.77	$ 70.60

Stock-Based Compensation Plan60

Stock-Based Compensation Plans - Restricted Stock and Performance Share Activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Shares, Beginning balance	383,978	432,138	435,989
Number of Restricted Shares, Granted	61,434	95,419	117,668
Number of Restricted Shares, Performance share pay-out	21,422	61,936	117,647
Number of Restricted Shares, Canceled	(4,590)	(12,786)	(3,845)
Number of Restricted Shares, Vested	(142,645)	(192,729)	(235,321)
Number of Restricted Shares, Ending balance	319,599	383,978	432,138
Weighted Average Grant Date Fair Value, Beginning balance	$ 71.50	$ 56.24	$ 41.83
Weighted Average Grant Date Fair Value, Ending balance	$ 88.77	$ 71.50	$ 56.24

Earnings Per Share - Computatio

Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share Basic And Diluted [Abstract]
Net income	$ 148,089	$ 126,172	$ 96,037
Basic weighted average shares outstanding	36,864	36,844	36,690
Dilutive effect of stock options and restricted stock	1,174	894	947
Diluted weighted average shares outstanding	38,038	37,738	37,637
Basic earnings per share	$ 4.02	$ 3.42	$ 2.62
Diluted earnings per share	$ 3.89	$ 3.34	$ 2.55

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	31,766	84,052	128,383

Credit Agreement - Additional I

Credit Agreement - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Oct. 31, 2017	Oct. 31, 2015	Dec. 31, 2017
Line Of Credit Facility [Line Items]
Revolving loans and letters of credit		$ 100,000,000
Letter of credit outstanding			$ 900,000
Additional Credit Agreement		$ 50,000,000
Amount available under credit agreement			$ 99,100,000
Period of credit agreement		2 years
Equity interest			65.00%
Minimum [Member]
Line Of Credit Facility [Line Items]
Excess judgments against the company			$ 10,000,000
Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Expiration period of credit agreement	Oct. 31, 2018
Period of credit agreement	1 year

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)AgreementSubsidiary	Dec. 31, 2016USD ($)ft²	Dec. 31, 2015USD ($)
Loss Contingencies [Line Items]
Non-cancelable leases expiration date	Dec. 31, 2033
Rental expense	$ 5,300	$ 4,000	$ 4,100
Number of lease agreements assigned to third parties | Agreement	1
Lease termination dates	2020-11
Future lease obligation under sublease arrangements	$ 800
Number of subsidiaries | Subsidiary	2
Settlement days of bond transaction	Within one to two trading days
Revenues from riskless principal transactions	$ 45,700	37,700	16,900
Collateral deposits	1,200	1,100
Clearing expenses	5,797	$ 6,060	$ 3,313
Lease Agreement [Member]
Loss Contingencies [Line Items]
Newly built office space | ft²		83,000
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Contingent obligation for standby letter of credit issued to Landlord	$ 900

Commitments and Contingencies65

Commitments and Contingencies - Summary of Minimum Rental Commitments under Operating Leases (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2,018	$ 5,000
2,019	9,659
2,020	10,770
2,021	10,149
2,022	9,129
2023 and thereafter	99,166
Operating Leases	$ 143,873

Segment and Geographic Inform66

Segment and Geographic Information - Additional Information (Detail) - Segment	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues From External Customers And Long Lived Assets [Line Items]
Number of operating segment	1
Geographic Concentration Risk [Member] | Total Revenue and Long-lived Assets [Member] | United Kingdom [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%

Segment and Geographic Inform67

Segment and Geographic Information - Summary of Revenue and Long-lived Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 397,471	$ 369,919	$ 303,098
Long-lived assets	38,548	31,104
United States [Member]
Segment Reporting Information [Line Items]
Revenues	336,867	314,343	262,558
Long-lived assets	27,990	23,370
United Kingdom [Member]
Segment Reporting Information [Line Items]
Revenues	59,151	54,015	39,338
Long-lived assets	10,532	7,713
Other [Member]
Segment Reporting Information [Line Items]
Revenues	1,453	1,561	$ 1,202
Long-lived assets	$ 26	$ 21

Retirement and Deferred Compe68

Retirement and Deferred Compensation Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Contribution to defined plans	$ 1,800,000	$ 1,900,000	$ 1,900,000
Non-qualified deferred cash incentive plan maximum eligibility percentage of employees	100.00%
Mutual fund investments and deferred compensation obligation, at fair value	$ 3,200,000	1,300,000
Trading gain and compensation expense	$ 400,000	$ 200,000	$ 0

Customer Concentration - Additi

Customer Concentration - Additional Information (Detail) - Customer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Number of client accounted for more than 10% of total revenue	0	0	0
Percentage of outstanding shares owned by single client	8.30%
Customer Concentration Risk [Member] | Trading Volume [Member]
Concentration Risk [Line Items]
Percentage of trading volumes by single client	12.20%	14.20%	15.30%