Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The taxable results of the Company’s U.S. operations are included in the consolidated income tax returns of Cowen, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings are submitted on a stand‑alone basis. These subsidiaries are subject to tax in their respective countries and the Company is responsible for and, thus, reports all taxes incurred by these subsidiaries. The countries where the Company owns subsidiaries that file tax returns are United Kingdom, Luxembourg, Malta, Gibraltar, Germany, Switzerland, South Africa, Canada and Hong Kong. The Company calculates its U.S. tax provision using the estimated annual effective tax rate methodology. The tax expense or benefit caused by an unusual or infrequent item is recorded in the quarter in which it occurs. To the extent that information is not available for the Company to fully determine the full year estimated impact of an item of income or tax adjustment, the Company calculates the tax impact of such item discretely. Accordingly, the Company uses the discrete methodology to calculate the income tax provision for its foreign subsidiaries and the tax impact of income attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds. Based on these methodologies, the Company’s effective income tax rate was 26.36% for the three months ended March 31, 2021. During the three months ended March 31, 2021, the items whose tax impact were recorded discretely related primarily to foreign taxes, as well as stock compensation. The Company's effective tax rate was 1.60% for the three months ended March 31, 2020. For the three months ended March 31, 2021, the effective tax rate differs from the statutory rate of 21% primarily due to income attributable to non-controlling interests in consolidated subsidiaries and investment funds, global intangible low-taxes income, stock compensation, as well as other nondeductible expenses. For the three months ended March 31, 2020, the effective tax rate differs from the statutory rate of 21% primarily due to losses attributable to non-controlling interests in consolidated subsidiaries and funds, foreign taxes, as well as other nondeductible expenses. As a result of the enactment of the American Rescue Plan Act signed on March 11, 2021, the Company is required to assess the tax impact of the Act in the quarter the law was enacted. Based on management analysis, there was no material impact on the Company's financial statements as of March 31, 2021. The Company maintained an uncertain tax position liability of $0.3 million as of March 31, 2021 and December 31, 2020 related to New York State tax matters. The Company records deferred tax assets and liabilities for the future tax benefit or expense that will result from differences between the carrying value of its assets for income tax purposes and for financial reporting purposes, as well as for operating or capital loss and tax credit carryovers. A valuation allowance is recorded to bring the net deferred tax assets to a level that, in management's view, is more likely than not to be realized in the foreseeable future. This level will be estimated based on a number of factors, especially the amount of net deferred tax assets of the Company that are actually expected to be realized, for tax purposes, in the foreseeable future. As of March 31, 2021, the Company recorded a valuation allowance against deferred tax assets related to its foreign tax credits and foreign net operating losses. The Company is subject to examination by the United States Internal Revenue Service as well as state, local and foreign tax authorities in jurisdictions where the Company has significant business operations, such as New York, United Kingdom, Luxembourg, Malta, Germany and Switzerland. Currently, the Company is under audit by New York State for the 2013 to 2017 tax years. Management is not expecting a material tax liability from these audits. The Company continues to permanently reinvest the capital and accumulated earnings of its subsidiaries in the United Kingdom, Malta, Germany, Switzerland, Canada, South Africa and Hong Kong.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.