Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to U.S. federal, state and local income tax at the rate applicable to corporations less the rate attributable to the noncontrolling interest in Virtu Financial. These noncontrolling interests are subject to U.S. taxation as partnerships. Accordingly, for the three and nine months ended September 30, 2018 and 2017, the income attributable to these noncontrolling interests is reported in the condensed consolidated statements of comprehensive income, but the related U.S. income tax expense attributable to these noncontrolling interests is not reported by the Company as it is the obligation of the individual partners. The Company’s provisions for (benefits from) income taxes and effective tax rates were $13.8 million and 46.9%, and $(6.5) million and 14.0% for the three months ended September 30, 2018 and 2017, respectively, and $75.3 million and 13.8%, and $(2.9) million and 16.7% for the nine months ended September 30, 2018 and 2017, respectively. Income tax expense is also affected by the differing effective tax rates in foreign, state and local jurisdictions where certain of the Company’s subsidiaries are subject to corporate taxation. Included in Other assets on the condensed consolidated statements of financial condition at September 30, 2018 and December 31, 2017 are current income tax receivables of $40.7 million and $115.2 million, respectively. The balance at September 30, 2018 primarily comprises income taxes due to the Company from federal, state and local, and foreign tax jurisdictions based on income before taxes, and the balance at December 31, 2017 primarily comprises the income tax benefit of KCG net operating losses that were generated prior to the Acquisition of KCG and are eligible to be carried back by the Company. Included in Accounts payable and accrued expenses and other liabilities on the condensed consolidated statements of financial condition at September 30, 2018 and December 31, 2017 are current tax liabilities of $16.0 million and $7.6 million, respectively. The balances primarily comprise income taxes owed to federal, state and local, and foreign tax jurisdictions based on income before taxes. Deferred income taxes arise primarily due to the amortization of the deferred tax assets recognized in connection with the IPO (Note 6 "Tax Receivable Agreements") and the Acquisition of KCG (Note 3 "Acquisition of KCG Holdings, Inc."), differences in the valuation of financial assets and liabilities, and other temporary differences arising from the deductibility of compensation and depreciation expenses in different time periods for book and income tax return purposes. There are no expiration dates on the deferred tax assets. The Company’s deferred tax asset at September 30, 2018 and December 31, 2017 includes an alternative minimum tax credit carryforward of $0.6 million and $0.6 million, respectively, which can be either refunded over a period of years or applied against future income tax liability pursuant to the 2017 Tax Act. The provisions of ASC 740 require that carrying amounts of deferred tax assets be reduced by a valuation allowance if, based on the available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Accordingly, the need to establish valuation allowances for deferred tax assets is assessed periodically with appropriate consideration given to all positive and negative evidence related to the realization of the deferred tax assets. As a result of the Acquisition of KCG, the Company has non-U.S. net operating losses at September 30, 2018 and December 31, 2017 of $231.8 million and $231.8 million, respectively, and has recorded a related deferred tax asset of $43.5 million and $43.5 million, respectively. A full valuation allowance was also recorded against this deferred tax asset at September 30, 2018 and December 31, 2017 as it is more likely than not that this deferred tax asset will not be realized. No valuation allowance against the remaining deferred taxes was recorded as of September 30, 2018 and December 31, 2017 because it is more likely than not that these deferred tax assets will be fully realized. The Company is subject to taxation in U.S. federal, state, local and foreign jurisdictions. As of September 30, 2018, the Company’s tax years for 2013 through 2017 and 2010 through 2017 are subject to examination by U.S. and non-U.S. tax authorities, respectively. As a result of the Acquisition of KCG, the Company has assumed any KCG tax exposures. KCG is currently subject to U.S. federal income tax examinations for 2013 through 2017, and to non-U.S. income tax examinations for the tax years 2007 through 2017. In addition, the Company is subject to state and local income tax examinations in various jurisdictions for the tax years 2007 through 2017. The final outcome of these examinations is not yet determinable. However, the Company anticipates that adjustments to the unrecognized tax benefits, if any, will not result in a material change to the financial condition, results of operations and cash flows. The 2017 Tax Act was signed into law on December 22, 2017 and significantly revises the U.S. corporate income tax by, among other things, lowering the statutory corporate tax rate from 35% to 21%, and eliminating certain deductions. As of December 31, 2017, the Company recorded a reduction of its deferred tax assets for the impact of the 2017 Tax Act of approximately $90.6 million, which was primarily composed of the remeasurement of federal net deferred tax assets as a result of the permanent reduction in the U.S. statutory corporate tax rate from 35% to 21%. During the first three quarters of 2018, the Company did not make any further adjustments due to the 2017 Tax Act. The Company has completed its determination of the accounting implications of the 2017 Tax act on its tax balances.

Income Taxes

The Company is subject to U.S. federal, state and local income tax at the rate applicable to corporations less the rate attributable to the noncontrolling interest in Virtu Financial. These noncontrolling interests are subject to U.S. taxation as partnerships. Accordingly, for the three and nine months ended September 30, 2018 and 2017, the income attributable to these noncontrolling interests is reported in the condensed consolidated statements of comprehensive income, but the related U.S. income tax expense attributable to these noncontrolling interests is not reported by the Company as it is the obligation of the individual partners. The Company’s provisions for (benefits from) income taxes and effective tax rates were $13.8 million and 46.9%, and $(6.5) million and 14.0% for the three months ended September 30, 2018 and 2017, respectively, and $75.3 million and 13.8%, and $(2.9) million and 16.7% for the nine months ended September 30, 2018 and 2017, respectively. Income tax expense is also affected by the differing effective tax rates in foreign, state and local jurisdictions where certain of the Company’s subsidiaries are subject to corporate taxation.

Included in Other assets on the condensed consolidated statements of financial condition at September 30, 2018 and December 31, 2017 are current income tax receivables of $40.7 million and $115.2 million, respectively. The balance at September 30, 2018 primarily comprises income taxes due to the Company from federal, state and local, and foreign tax jurisdictions based on income before taxes, and the balance at December 31, 2017 primarily comprises the income tax benefit of KCG net operating losses that were generated prior to the Acquisition of KCG and are eligible to be carried back by the Company. Included in Accounts payable and accrued expenses and other liabilities on the condensed consolidated statements of financial condition at September 30, 2018 and December 31, 2017 are current tax liabilities of $16.0 million and $7.6 million, respectively. The balances primarily comprise income taxes owed to federal, state and local, and foreign tax jurisdictions based on income before taxes.

Deferred income taxes arise primarily due to the amortization of the deferred tax assets recognized in connection with the IPO (Note 6 "Tax Receivable Agreements") and the Acquisition of KCG (Note 3 "Acquisition of KCG Holdings, Inc."), differences in the valuation of financial assets and liabilities, and other temporary differences arising from the deductibility of compensation and depreciation expenses in different time periods for book and income tax return purposes.

There are no expiration dates on the deferred tax assets. The Company’s deferred tax asset at September 30, 2018 and December 31, 2017 includes an alternative minimum tax credit carryforward of $0.6 million and $0.6 million, respectively, which can be either refunded over a period of years or applied against future income tax liability pursuant to the 2017 Tax Act. The provisions of ASC 740 require that carrying amounts of deferred tax assets be reduced by a valuation allowance if, based on the available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. Accordingly, the need to establish valuation allowances for deferred tax assets is assessed periodically with appropriate consideration given to all positive and negative evidence related to the realization of the deferred tax assets. As a result of the Acquisition of KCG, the Company has non-U.S. net operating losses at September 30, 2018 and December 31, 2017 of $231.8 million and $231.8 million, respectively, and has recorded a related deferred tax asset of $43.5 million and $43.5 million, respectively. A full valuation allowance was also recorded against this deferred tax asset at September 30, 2018 and December 31, 2017 as it is more likely than not that this deferred tax asset will not be realized. No valuation allowance against the remaining deferred taxes was recorded as of September 30, 2018 and December 31, 2017 because it is more likely than not that these deferred tax assets will be fully realized.

The Company is subject to taxation in U.S. federal, state, local and foreign jurisdictions. As of September 30, 2018, the Company’s tax years for 2013 through 2017 and 2010 through 2017 are subject to examination by U.S. and non-U.S. tax authorities, respectively. As a result of the Acquisition of KCG, the Company has assumed any KCG tax exposures. KCG is currently subject to U.S. federal income tax examinations for 2013 through 2017, and to non-U.S. income tax examinations for the tax years 2007 through 2017. In addition, the Company is subject to state and local income tax examinations in various jurisdictions for the tax years 2007 through 2017. The final outcome of these examinations is not yet determinable. However, the Company anticipates that adjustments to the unrecognized tax benefits, if any, will not result in a material change to the financial condition, results of operations and cash flows.

The 2017 Tax Act was signed into law on December 22, 2017 and significantly revises the U.S. corporate income tax by, among other things, lowering the statutory corporate tax rate from 35% to 21%, and eliminating certain deductions. As of December 31, 2017, the Company recorded a reduction of its deferred tax assets for the impact of the 2017 Tax Act of approximately $90.6 million, which was primarily composed of the remeasurement of federal net deferred tax assets as a result of the permanent reduction in the U.S. statutory corporate tax rate from 35% to 21%. During the first three quarters of 2018, the Company did not make any further adjustments due to the 2017 Tax Act. The Company has completed its determination of the accounting implications of the 2017 Tax act on its tax balances.