Schedule I - Condensed Financial Information of Registrant - Condensed Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	3 Months Ended							11 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2019	Aug. 31, 2019	May 31, 2019	Feb. 28, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2019	Dec. 31, 2017
Revenues:
Revenues									$ 5,009,728		$ 5,358,656	$ 5,048,906
Expenses:
Compensation and benefits									1,862,782		1,824,891	1,950,935
Interest expense									89,249		87,177	101,202
Selling, general and other expenses									961,328		1,009,643	778,052
Total expenses									3,524,957	$ 3,336,359	3,617,363	3,396,042
Income (loss) related to associated companies									57,023	(76,864)	202,995	(74,901)
Income tax benefit									19,008	195,550	(483,955)	642,286
Income (loss) from continuing operations									285,475		959,593	(36,003)
Preferred stock dividends	$ (851)	$ (1,276)	$ (1,275)	$ (1,276)	$ (1,276)	$ (1,276)	$ (1,171)	$ (1,172)	(4,470)		(5,103)	(4,375)
Net income attributable to Jefferies Financial Group Inc. common shareholders	$ (20,371)	$ 195,541	$ 48,477	$ 670,764	$ 44,811	$ 192,635	$ 725,529	$ 124,525	$ 1,022,318	$ 610,277	$ 959,593	$ 167,351
Basic earnings (loss) per common share attributable to Jefferies Financial Group Inc. common shareholders:
Income (loss) from continuing operations (USD per share)	$ (0.06)					$ 0.56	$ 0.08	$ 0.23	$ 0.82	$ 1.14	$ 3.07	$ (0.10)
Income from discontinued operations (USD per share)	0					0	0.15	0.11	0.27		0	0.55
Gain on disposal of discontinued operations (USD per share)	0					0	1.82	0	1.84		0	0
Net income (USD per share)	(0.06)	$ 0.63	$ 0.16	$ 2.17	$ 0.14	0.56	2.05	0.34	2.93	1.65	3.07	0.45
Diluted earnings (loss) per common share attributable to Jefferies Financial Group Inc. common shareholders:
Income from continuing operations (USD per share)	(0.06)					0.55	0.08	0.23	0.81	1.13	3.03	(0.10)
Income from discontinued operations (USD per share)	0					0	0.15	0.11	0.26		0	0.55
Gain on disposal of discontinued operations (USD per share)	0					0	1.80	0	1.83		0	0
Net income (USD per share)	$ (0.06)	$ 0.62	$ 0.15	$ 2.14	$ 0.14	$ 0.55	$ 2.03	$ 0.34	$ 2.90	$ 1.63	$ 3.03	$ 0.45
Parent Company
Revenues:
Revenues									$ 121,549		$ 9,102	$ (9,477)
Expenses:
Compensation and benefits									49,955		61,920	47,462
WilTel pension expense									2,659		2,594	2,957
Interest expense									54,090		53,048	58,943
Intercompany interest expense									3,642		0	361,446
Selling, general and other expenses									21,664		23,062	20,821
Total expenses									132,010		140,624	491,629
Loss from continuing operations before income taxes, income related to associated companies and equity in earnings of subsidiaries									(10,461)		(131,522)	(501,106)
Income (loss) related to associated companies									96,808		229,320	3,183
Income (loss) from continuing operations before income taxes and equity in earnings of subsidiaries									86,347		97,798	(497,923)
Income tax benefit									(5,281)		(523,310)	(47,329)
Income (loss) from continuing operations before equity in earnings of subsidiaries									91,628		621,108	(450,594)
Equity in earnings from continuing operations of subsidiaries, net of taxes									198,317		343,588	418,966
Income (loss) from continuing operations									289,945		964,696	(31,628)
Equity in earnings from discontinued operations of subsidiaries, net of taxes									92,922		0	203,354
Gain on disposal of discontinued operations, net of taxes									643,921		0	0
Net income									1,026,788		964,696	171,726
Preferred stock dividends									(4,470)		(5,103)	(4,375)
Net income attributable to Jefferies Financial Group Inc. common shareholders									$ 1,022,318		$ 959,593	$ 167,351
Basic earnings (loss) per common share attributable to Jefferies Financial Group Inc. common shareholders:
Income (loss) from continuing operations (USD per share)									$ 0.82		$ 3.07	$ (0.10)
Income from discontinued operations (USD per share)									0.27		0	0.55
Gain on disposal of discontinued operations (USD per share)									1.84		0	0
Net income (USD per share)									2.93		3.07	0.45
Diluted earnings (loss) per common share attributable to Jefferies Financial Group Inc. common shareholders:
Income from continuing operations (USD per share)									0.81		3.03	(0.10)
Income from discontinued operations (USD per share)									0.26		0	0.55
Gain on disposal of discontinued operations (USD per share)									1.83		0	0
Net income (USD per share)									$ 2.90		$ 3.03	$ 0.45
Principal transactions
Revenues:
Revenues									$ 232,224		$ 559,300	$ 923,418
Principal transactions | Parent Company
Revenues:
Revenues									120,886		(246,101)	(9,754)
Gain on sale of equity interest in National Beef | Parent Company
Revenues:
Revenues									0		205,017	0
Other
Revenues:
Revenues									558,336		667,993	424,788
Other | Parent Company
Revenues:
Revenues									$ 663		$ 50,186	$ 277