Loans to and Investments in Associated Companies (Schedule of Loans to and Investments In Associated Companies) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2020	Aug. 31, 2019
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			$ 1,652,957	$ 2,417,332
Income (losses) related to associated companies	$ 5,053	$ 72,283	(69,523)	121,766
Income (losses) related to Jefferies associated companies	3,854	17,293	(22,282)	71,614
Contributions to (distributions from) associated companies, net			(29,553)	(110,465)
Other			7,757	(153,950)
Loans to and investments in associated companies as of end of period	1,539,356	2,346,297	1,539,356	2,346,297
Jefferies Finance
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			673,867	728,560
Income (losses) related to associated companies			0	0
Income (losses) related to Jefferies associated companies	(17,731)	(6,901)	(65,681)	1,035
Contributions to (distributions from) associated companies, net			10,107	(58,682)
Other			0	0
Loans to and investments in associated companies as of end of period	618,293	670,913	618,293	670,913
Berkadia
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			268,949	245,228
Income (losses) related to associated companies			0	0
Income (losses) related to Jefferies associated companies	18,448	24,286	40,373	72,231
Contributions to (distributions from) associated companies, net			(36,615)	(47,682)
Other			510	722
Loans to and investments in associated companies as of end of period	273,217	270,499	273,217	270,499
National Beef
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period				653,630
Income (losses) related to associated companies	0	75,867	0	137,918
Income (losses) related to Jefferies associated companies				0
Contributions to (distributions from) associated companies, net				(72,767)
Other				(10)
Loans to and investments in associated companies as of end of period		718,771		718,771
FXCM
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			70,223	75,031
Income (losses) related to associated companies	3,704	(573)	9,956	(5,589)
Income (losses) related to Jefferies associated companies			0	0
Contributions to (distributions from) associated companies, net			0	3,500
Other			161	(134)
Loans to and investments in associated companies as of end of period	80,340	72,808	80,340	72,808
Linkem
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			194,847	165,157
Income (losses) related to associated companies	(1,945)	(12,115)	(21,754)	(20,696)
Income (losses) related to Jefferies associated companies			0	0
Contributions to (distributions from) associated companies, net			35,103	82,178
Other			(2,149)	(8,226)
Loans to and investments in associated companies as of end of period	206,047	218,413	206,047	218,413
HomeFed
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period				337,542
Income (losses) related to associated companies	0	8,419	0	7,902
Income (losses) related to Jefferies associated companies				0
Contributions to (distributions from) associated companies, net				0
Other				(345,444)
Loans to and investments in associated companies as of end of period		0		0
Real estate associated companies
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			255,309	87,074
Income (losses) related to associated companies	2,532	464	(50,910)	1,536
Income (losses) related to Jefferies associated companies			0	0
Contributions to (distributions from) associated companies, net			(34,505)	(3,054)
Other			0	198,273
Loans to and investments in associated companies as of end of period	169,894	283,829	169,894	283,829
Other
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			189,762	125,110
Income (losses) related to associated companies	762	221	(6,815)	695
Income (losses) related to Jefferies associated companies	3,137	(92)	3,026	(1,652)
Contributions to (distributions from) associated companies, net			(3,643)	(13,958)
Other			9,235	869
Loans to and investments in associated companies as of end of period	191,565	$ 111,064	191,565	$ 111,064
Linkem and Other \| Loans and debt securities
Equity Method Investment [Roll Forward]
Loans to and investments in associated companies as of beginning of period			70,200
Loans to and investments in associated companies as of end of period	$ 100,200		100,200
Brooklyn Renaissance Plaza and Hotel \| HomeFed
Equity Method Investment [Roll Forward]
Equity method investment, other than temporary impairment			6,900
RedSky JZ Fulton Mall \| HomeFed
Equity Method Investment [Roll Forward]
Equity method investment, other than temporary impairment			$ 55,600

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