Significant Accounting Policies	6 Months Ended
Jun. 30, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated. These consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. The consolidated financial information as of December 31, 2014 has been derived from audited financial statements not included herein. These unaudited consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) with respect to Form 10-Q and reflect all adjustments that, in the opinion of management, are normal and recurring, and that are necessary for a fair statement of the results for the interim periods presented. In accordance with such rules and regulations, certain disclosures that are normally included in annual financial statements have been omitted. Interim period operating results may not be indicative of the operating results for a full year. 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. Securities Available-for-Sale The Company classifies its marketable securities as available-for-sale securities. Unrealized marketable securities gains and losses, net of taxes, are included in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Realized gains and losses are recorded in the Consolidated Statements of Operations in other revenues. For the purpose of computing realized gains and losses, cost is determined on a specific identification basis. The Company assesses whether an other-than-temporary impairment loss on the 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 six months ended June 30, 2015 and 2014. 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 portfolio and foreign currency forward contracts. All other financial instruments are short-term in nature and the carrying amount is reported in the Consolidated Statements of Financial Condition 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. 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 clearance 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 and post-trade services. The Company generates revenue from information services provided to our broker-dealer clients, institutional investor clients and data-only subscribers. Information services are invoiced monthly, quarterly or annually. When billed in advance, revenues are deferred and recognized monthly on a straight-line basis. The Company also generates revenue from regulatory transaction reporting and trade matching services. Revenue is recognized in the period the services are provided. Technology products and services. The Company generates revenues from professional consulting services, technology software licenses and maintenance and support services (referred to as post-contract technical support or “PCS”). Revenue is generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collection is considered probable. The Company enters into time and materials professional consulting contracts unrelated to any software product. Revenue for time and materials contracts is recognized as services are performed. The Company generally sells software license subscriptions on a stand-alone basis or software licenses and PCS together as part of multiple-element arrangements. Revenue for software license subscriptions is recognized ratably over the contract period. For arrangements that include multiple elements, generally software licenses and PCS, the Company allocates and defers revenue for the undelivered items based on vendor specific objective evidence (“VSOE”) of the fair value of the undelivered elements and recognizes the difference between the total arrangement fee and the amount deferred for the undelivered items as license revenue. When VSOE does not exist for undelivered items, the entire arrangement fee is recognized ratably over the performance period. For PCS, the term is typically one year and revenue is recognized over the duration of the arrangement on a straight-line basis. Initial set-up fees. The Company enters into agreements with its broker-dealer clients pursuant to which the Company provides access to its platform through a non-exclusive and non-transferable license. Broker-dealer clients may pay an initial set-up fee, which is typically due and payable upon execution of a dealer agreement. The initial set-up fee, if any, varies by agreement. Revenue is recognized over the initial term of the agreement, which is generally two years. Initial set-up fees are reported in other income in the Consolidated Statements of Operations. 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. 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. 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. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) No. 2014-09, “Revenue from Contracts with Customers”, which will replace most of the existing revenue recognition guidance in GAAP. The core principle of the ASU is that an entity should 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 ASU requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments. The ASU will be effective for the Company beginning January 1, 2018 and allows for both retrospective and prospective methods of adoption. The Company is in the process of determining the method of adoption and assessing the impact of this ASU on the Company’s Consolidated Financial Statements.

2. Significant Accounting Policies

Basis of Presentation

The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany transactions and balances have been eliminated. These consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. The consolidated financial information as of December 31, 2014 has been derived from audited financial statements not included herein. These unaudited consolidated financial statements are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) with respect to Form 10-Q and reflect all adjustments that, in the opinion of management, are normal and recurring, and that are necessary for a fair statement of the results for the interim periods presented. In accordance with such rules and regulations, certain disclosures that are normally included in annual financial statements have been omitted. Interim period operating results may not be indicative of the operating results for a full year.

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.

Securities Available-for-Sale

The Company classifies its marketable securities as available-for-sale securities. Unrealized marketable securities gains and losses, net of taxes, are included in accumulated other comprehensive loss in the Consolidated Statements of Financial Condition. Realized gains and losses are recorded in the Consolidated Statements of Operations in other revenues. For the purpose of computing realized gains and losses, cost is determined on a specific identification basis.

The Company assesses whether an other-than-temporary impairment loss on the 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 six months ended June 30, 2015 and 2014.

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 portfolio and foreign currency forward contracts. All other financial instruments are short-term in nature and the carrying amount is reported in the Consolidated Statements of Financial Condition 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.

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 clearance 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 and post-trade services. The Company generates revenue from information services provided to our broker-dealer clients, institutional investor clients and data-only subscribers. Information services are invoiced monthly, quarterly or annually. When billed in advance, revenues are deferred and recognized monthly on a straight-line basis. The Company also generates revenue from regulatory transaction reporting and trade matching services. Revenue is recognized in the period the services are provided.

Technology products and services. The Company generates revenues from professional consulting services, technology software licenses and maintenance and support services (referred to as post-contract technical support or “PCS”). Revenue is generally recognized when persuasive evidence of an arrangement exists, delivery has occurred, the fee is fixed or determinable and collection is considered probable.

The Company enters into time and materials professional consulting contracts unrelated to any software product. Revenue for time and materials contracts is recognized as services are performed. The Company generally sells software license subscriptions on a stand-alone basis or software licenses and PCS together as part of multiple-element arrangements. Revenue for software license subscriptions is recognized ratably over the contract period. For arrangements that include multiple elements, generally software licenses and PCS, the Company allocates and defers revenue for the undelivered items based on vendor specific objective evidence (“VSOE”) of the fair value of the undelivered elements and recognizes the difference between the total arrangement fee and the amount deferred for the undelivered items as license revenue. When VSOE does not exist for undelivered items, the entire arrangement fee is recognized ratably over the performance period. For PCS, the term is typically one year and revenue is recognized over the duration of the arrangement on a straight-line basis.

Initial set-up fees. The Company enters into agreements with its broker-dealer clients pursuant to which the Company provides access to its platform through a non-exclusive and non-transferable license. Broker-dealer clients may pay an initial set-up fee, which is typically due and payable upon execution of a dealer agreement. The initial set-up fee, if any, varies by agreement. Revenue is recognized over the initial term of the agreement, which is generally two years. Initial set-up fees are reported in other income in the Consolidated Statements of Operations.

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.

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.

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.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update (“ASU”) No. 2014-09, “Revenue from Contracts with Customers”, which will replace most of the existing revenue recognition guidance in GAAP. The core principle of the ASU is that an entity should 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 ASU requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments. The ASU will be effective for the Company beginning January 1, 2018 and allows for both retrospective and prospective methods of adoption. The Company is in the process of determining the method of adoption and assessing the impact of this ASU on the Company’s Consolidated Financial Statements.