Loans To And Investments In Associated Companies (Schedule Of Loans to and Investments In Associated Companies) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			$ 1,757,369	$ 1,712,568
Income (losses) related to associated companies	$ 51,890	$ 29,807	71,942	70,258
Income (losses) related to associated companies classified as other revenues	(7,836)	28,457	(31,252)	49,146
Contributions to (distributions from) associated companies, net			(64,632)	(136,645)
Equity Method Investments Other Activity, Net			3,910	(13,855)
Loans to and investments in associated companies, ending balance	1,737,337	1,681,472	1,737,337	1,681,472
Noncontrolling interests	178,040		178,040		$ 64,679
Jefferies Finance [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			528,575	508,891
Income (losses) related to associated companies			0	0
Income (losses) related to associated companies classified as other revenues	(15,675)	20,220	(38,481)	31,531
Contributions to (distributions from) associated companies, net			(19,300)	(40,500)
Equity Method Investments Other Activity, Net			0	1
Loans to and investments in associated companies, ending balance	470,794	499,923	470,794	499,923
Jefferies LoanCore [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			288,741	258,947
Income (losses) related to associated companies			0	0
Income (losses) related to associated companies classified as other revenues	8,201	8,236	8,014	18,094
Contributions to (distributions from) associated companies, net			(138,622)	(36,126)
Equity Method Investments Other Activity, Net			0	0
Loans to and investments in associated companies, ending balance	158,133	240,915	158,133	240,915
Berkadia [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			190,986	208,511
Income (losses) related to associated companies	20,398	19,733	33,452	52,076
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			(40,748)	(50,152)
Equity Method Investments Other Activity, Net			207	(3,432)
Loans to and investments in associated companies, ending balance	183,897	207,003	183,897	207,003
Garcadia [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			172,660	167,939
Income (losses) related to associated companies	13,941	15,881	29,268	31,134
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			(14,777)	(29,859)
Equity Method Investments Other Activity, Net			0	0
Loans to and investments in associated companies, ending balance	187,151	169,214	187,151	169,214
Linkem [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			150,149	159,054
Income (losses) related to associated companies	(6,673)	(4,354)	(14,873)	(9,142)
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			33,297	6,931
Equity Method Investments Other Activity, Net			3,462	(10,577)
Loans to and investments in associated companies, ending balance	172,035	146,266	172,035	146,266
HomeFed Corporation [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			275,378	271,782
Income (losses) related to associated companies	23,634	(954)	22,346	(3,052)
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			0	0
Equity Method Investments Other Activity, Net			0	0
Loans to and investments in associated companies, ending balance	297,724	268,730	297,724	268,730
Golden Queen Mining Company, LLC [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			114,323	103,598
Income (losses) related to associated companies	(1,309)	(712)	(1,664)	(999)
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			0	12,500
Equity Method Investments Other Activity, Net			0	0
Loans to and investments in associated companies, ending balance	112,659	115,099	112,659	115,099
Noncontrolling interests	33,200		33,200		$ 33,700
54 Madison [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			0	0
Income (losses) related to associated companies	1,256	0	2,483	0
Income (losses) related to associated companies classified as other revenues			0	0
Contributions to (distributions from) associated companies, net			115,499	0
Equity Method Investments Other Activity, Net			3,642	0
Loans to and investments in associated companies, ending balance	121,624	0	121,624	0
Noncontrolling interests	72,400		72,400
Other [Member]
Loans to and Investments in Associated Companies Rollforward [Roll Forward]
Loans to and investments in associated companies, beginning balance			36,557	33,846
Income (losses) related to associated companies	643	213	930	241
Income (losses) related to associated companies classified as other revenues	(362)	1	(785)	(479)
Contributions to (distributions from) associated companies, net			19	561
Equity Method Investments Other Activity, Net			(3,401)	153
Loans to and investments in associated companies, ending balance	$ 33,320	$ 34,322	$ 33,320	$ 34,322