Income Taxes	9 Months Ended
Sep. 30, 2014
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 Group, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings have to be 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, Gibraltar, 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. The Company uses the discrete methodology to calculate its income tax provision for its foreign subsidiaries. Based on these methodologies, the Company’s effective income tax rate was 0.69% and 2.22% for the nine months ended September 30, 2014 and 2013, respectively. During the nine months ended September 30, 2014, the unusual or infrequent item whose tax impact was recorded discretely primarily related to the tax provisions of the Company’s foreign subsidiaries. For the nine months ended September 30, 2014 and 2013, the effective tax rate differs from the statutory rate of 35% primarily due to a change in the Company's valuation allowance, stock compensation and other nondeductible expenses. 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. Deferred tax liabilities that cannot be realized in a similar future time period and thus that cannot offset the Company’s deferred tax assets are not taken into account when calculating the Company’s net deferred tax assets. The Company weighs all positive and negative evidence to reach its conclusion to record a full or partial valuation allowance for its deferred tax assets. Positive factors include sustainability of profitable operations, carry-forward periods for net operating losses and the effect of reversing taxable temporary differences, while negative factors include the Company’s three-year cumulative loss position, which is heavily weighted. Based on this analysis, the Company has recorded a valuation allowance against substantially all of its net deferred tax assets as of September 30, 2014. Due to recent and current positive operating results and, because the losses from 2011 are rolled off from the three-year rolling analysis, the Company anticipates to be in a three-year cumulative income position later in 2014. As a result of this development and other positive factors as indicated above, it is possible that the Company could release a large part of the Company’s valuation allowance in the fourth quarter of 2014, which would have a material and favorable effect on Net income and Stockholders’ equity. At September 30, 2014, the Company’s valuation allowance was $137.4 million, of which $135.2 million is related to the Company’s US operations. The Company is subject to examination by the United States Internal Revenue Service, the United Kingdom Inland Revenue Service as well as state, local and foreign tax authorities in jurisdictions where the Company has significant business operations, such as New York. Currently, the Company is under audit by New York State for the 2009-2012 tax years. The Company does not expect to incur material tax liabilities from these audits. The Company intends to permanently reinvest the capital and accumulated earnings of its foreign subsidiaries in the respective subsidiary, but remits the current earnings of its foreign subsidiaries to the United States to the extent permissible under local regulatory rules. The undistributed earnings of the Company’s foreign subsidiaries totaled $1.0 million and $1.2 million as of September 30, 2014 and September 30, 2013, respectively, and the tax liability that would arise if these earnings were remitted to the United States would be approximately $0.2 million and $0.1 million, respectively.

Income Taxes

The taxable results of the Company’s U.S. operations are included in the consolidated income tax returns of Cowen Group, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings have to be 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, Gibraltar, 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. The Company uses the discrete methodology to calculate its income tax provision for its foreign subsidiaries. Based on these methodologies, the Company’s effective income tax rate was 0.69% and 2.22% for the nine months ended September 30, 2014 and 2013, respectively. During the nine months ended September 30, 2014, the unusual or infrequent item whose tax impact was recorded discretely primarily related to the tax provisions of the Company’s foreign subsidiaries.

For the nine months ended September 30, 2014 and 2013, the effective tax rate differs from the statutory rate of 35% primarily due to a change in the Company's valuation allowance, stock compensation and other nondeductible expenses.

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. Deferred tax liabilities that cannot be realized in a similar future time period and thus that cannot offset the Company’s deferred tax assets are not taken into account when calculating the Company’s net deferred tax assets. The Company weighs all positive and negative evidence to reach its conclusion to record a full or partial valuation allowance for its deferred tax assets. Positive factors include sustainability of profitable operations, carry-forward periods for net operating losses and the effect of reversing taxable temporary differences, while negative factors include the Company’s three-year cumulative loss position, which is heavily weighted. Based on this analysis, the Company has recorded a valuation allowance against substantially all of its net deferred tax assets as of September 30, 2014. Due to recent and current positive operating results and, because the losses from 2011 are rolled off from the three-year rolling analysis, the Company anticipates to be in a three-year cumulative income position later in 2014. As a result of this development and other positive factors as indicated above, it is possible that the Company could release a large part of the Company’s valuation allowance in the fourth quarter of 2014, which would have a material and favorable effect on Net income and Stockholders’ equity. At September 30, 2014, the Company’s valuation allowance was $137.4 million, of which $135.2 million is related to the Company’s US operations.

The Company is subject to examination by the United States Internal Revenue Service, the United Kingdom Inland Revenue Service as well as state, local and foreign tax authorities in jurisdictions where the Company has significant business operations, such as New York. Currently, the Company is under audit by New York State for the 2009-2012 tax years. The Company does not expect to incur material tax liabilities from these audits.

The Company intends to permanently reinvest the capital and accumulated earnings of its foreign subsidiaries in the respective subsidiary, but remits the current earnings of its foreign subsidiaries to the United States to the extent permissible under local regulatory rules. The undistributed earnings of the Company’s foreign subsidiaries totaled $1.0 million and $1.2 million as of September 30, 2014 and September 30, 2013, respectively, and the tax liability that would arise if these earnings were remitted to the United States would be approximately $0.2 million and $0.1 million, respectively.