Income Taxes	9 Months Ended
Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The aggregate amount of gross unrecognized tax benefits related to uncertain tax positions at September 30, 2018 was $237.8 million (including $63.0 million for interest), of which $184.0 million related to Jefferies Group. The aggregate amount of gross unrecognized tax benefits related to uncertain tax positions at December 31, 2017 was $226.4 million (including $57.4 million for interest), of which $177.8 million related to Jefferies Group. If recognized, such amounts would lower our effective tax rate. Accrued interest is included in Payables, expense accruals and other liabilities in the Consolidated Statements of Financial Condition. No material penalties were accrued for the nine months ended September 30, 2018 and the year ended December 31, 2017. The statute of limitations with respect to our federal income tax returns has expired for all years through 2013. We have settled our 2013 Internal Revenue Service examination with the settlement having an immaterial impact on our effective tax rate. Our New York State and New York City income tax returns are currently being audited for the 2012 to 2014 period and 2011 to 2014 period, respectively. Prior to becoming a wholly-owned subsidiary, Jefferies Group filed a consolidated U.S. federal income tax return with its qualifying subsidiaries and was subject to income tax in various states, municipalities and foreign jurisdictions. Jefferies Group is currently under examination by various major tax jurisdictions. We do not expect that resolution of these examinations will have a significant effect on our Consolidated Statements of Financial Condition, but could have a significant impact on the Consolidated Statements of Operations for the period in which resolution occurs. Our provision for income taxes for continuing operations for the nine months ended September 30, 2018 was reduced by a $43.9 million benefit resulting from a reversal of our valuation allowance with respect to certain federal and state net operating loss carryforwards ("NOLs") which we now believe are more likely than not to be utilized before they expire. Our provision for income taxes from continuing operations for the nine months ended September 30, 2017 was reduced by a $31.9 million benefit resulting from the repatriation of Jefferies Group's earnings from certain of its foreign subsidiaries, along with their associated foreign tax credits. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118"), which provides guidance on accounting for the tax effects of the Tax Cuts and Jobs Act (the "Tax Act"). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under Accounting Standards Codification 740, Income Taxes ("ASC 740"). While the initial estimated impact of the Tax Act was calculated using all available information, we anticipate modifications based on the procedures set forth under SAB 118. This process is applied at each reporting period to account for and qualitatively disclose: (1) the effects of the change in tax law for which accounting is complete; (2) provisional amounts (or adjustments to provisional amounts) for the effects of the tax law where accounting is not complete, but that a reasonable estimate has been determined; and (3) where a reasonable estimate cannot yet be made, taxes are reflected in accordance with the law prior to the enactment of the Tax Act. Due to the complex nature of the Tax Act, we have not completed our accounting for the income tax effects of certain elements of the Tax Act. If we were able to make reasonable estimates of the effects of certain elements for which our analysis is not yet complete, we recorded a provisional estimate in the financial statements. If we were not yet able to make reasonable estimates of the impact of certain elements, we have not recorded any adjustments related to those elements and have continued accounting for them in accordance with ASC 740 on the basis of the tax laws in effect before the Tax Act. The ultimate impact of the Tax Act may differ from this estimate, possibly materially, due to refinement of our calculations based on updated information, changes in interpretations and assumptions, and guidance that may be issued and actions we may take in response to the Tax Act. We note that the Tax Act is complex and we continue to assess the impact that various provisions will have on our business. Since the Tax Act was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretation are expected, we consider the accounting for the deferred tax asset remeasurements, the transition tax, and other items to be incomplete due to the forthcoming guidance and our ongoing analysis of final year-end data and tax positions. During the nine months ended September 30, 2018, we revised our prior estimate and recorded a $3.8 million increase in our tax expense related to the Tax Act.

Income Taxes

The aggregate amount of gross unrecognized tax benefits related to uncertain tax positions at September 30, 2018 was $237.8 million (including $63.0 million for interest), of which $184.0 million related to Jefferies Group. The aggregate amount of gross unrecognized tax benefits related to uncertain tax positions at December 31, 2017 was $226.4 million (including $57.4 million for interest), of which $177.8 million related to Jefferies Group. If recognized, such amounts would lower our effective tax rate. Accrued interest is included in Payables, expense accruals and other liabilities in the Consolidated Statements of Financial Condition. No material penalties were accrued for the nine months ended September 30, 2018 and the year ended December 31, 2017.

The statute of limitations with respect to our federal income tax returns has expired for all years through 2013. We have settled our 2013 Internal Revenue Service examination with the settlement having an immaterial impact on our effective tax rate. Our New York State and New York City income tax returns are currently being audited for the 2012 to 2014 period and 2011 to 2014 period, respectively. Prior to becoming a wholly-owned subsidiary, Jefferies Group filed a consolidated U.S. federal income tax return with its qualifying subsidiaries and was subject to income tax in various states, municipalities and foreign jurisdictions. Jefferies Group is currently under examination by various major tax jurisdictions. We do not expect that resolution of these examinations will have a significant effect on our Consolidated Statements of Financial Condition, but could have a significant impact on the Consolidated Statements of Operations for the period in which resolution occurs.

Our provision for income taxes for continuing operations for the nine months ended September 30, 2018 was reduced by a $43.9 million benefit resulting from a reversal of our valuation allowance with respect to certain federal and state net operating loss carryforwards ("NOLs") which we now believe are more likely than not to be utilized before they expire. Our provision for income taxes from continuing operations for the nine months ended September 30, 2017 was reduced by a $31.9 million benefit resulting from the repatriation of Jefferies Group's earnings from certain of its foreign subsidiaries, along with their associated foreign tax credits.

On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118"), which provides guidance on accounting for the tax effects of the Tax Cuts and Jobs Act (the "Tax Act"). SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under Accounting Standards Codification 740, Income Taxes ("ASC 740"). While the initial estimated impact of the Tax Act was calculated using all available information, we anticipate modifications based on the procedures set forth under SAB 118. This process is applied at each reporting period to account for and qualitatively disclose: (1) the effects of the change in tax law for which accounting is complete; (2) provisional amounts (or adjustments to provisional amounts) for the effects of the tax law where accounting is not complete, but that a reasonable estimate has been determined; and (3) where a reasonable estimate cannot yet be made, taxes are reflected in accordance with the law prior to the enactment of the Tax Act.

Due to the complex nature of the Tax Act, we have not completed our accounting for the income tax effects of certain elements of the Tax Act. If we were able to make reasonable estimates of the effects of certain elements for which our analysis is not yet complete, we recorded a provisional estimate in the financial statements. If we were not yet able to make reasonable estimates of the impact of certain elements, we have not recorded any adjustments related to those elements and have continued accounting for them in accordance with ASC 740 on the basis of the tax laws in effect before the Tax Act. The ultimate impact of the Tax Act may differ from this estimate, possibly materially, due to refinement of our calculations based on updated information, changes in interpretations and assumptions, and guidance that may be issued and actions we may take in response to the Tax Act. We note that the Tax Act is complex and we continue to assess the impact that various provisions will have on our business. Since the Tax Act was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretation are expected, we consider the accounting for the deferred tax asset remeasurements, the transition tax, and other items to be incomplete due to the forthcoming guidance and our ongoing analysis of final year-end data and tax positions. During the nine months ended September 30, 2018, we revised our prior estimate and recorded a $3.8 million increase in our tax expense related to the Tax Act.