Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	May 31, 2019	Jun. 30, 2018	May 31, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 672,276	$ 748,944	$ 719,291	$ 888,093
Other comprehensive income (loss):
Net unrealized holding gains (losses) on investments arising during the period, net of income tax provision (benefit) of $31, $227, $138 and $(143)	62	818	379	(408)
Less: reclassification adjustment for net (gains) losses included in net income, net of income tax provision (benefit) of $(544,677), $42, $(545,054) and $37	(544,307)	(118)	(543,178)	(103)
Net change in unrealized holding gains (losses) on investments, net of income tax provision (benefit) of $544,708, $185, $545,192 and $(180)	(544,245)	700	(542,799)	(511)
Net unrealized foreign exchange gains (losses) arising during the period, net of income tax provision (benefit) of $(10,439), $(2,719), $(2,717) and $(793)	(40,147)	(49,310)	(9,193)	(31,407)
Less: reclassification adjustment for foreign exchange (gains) losses included in net income, net of income tax provision (benefit) of $0, $(16), $0 and $(16)	0	(20,459)	0	(20,459)
Net change in unrealized foreign exchange gains (losses), net of income tax provision (benefit) of $(10,439), $(2,703), $(2,717) and $(777)	(40,147)	(69,769)	(9,193)	(51,866)
Net unrealized gains (losses) on instrument specific credit risk arising during the period, net of income tax provision (benefit) of $858, $8,875, $6,807 and $4,241	2,616	26,287	20,151	14,718
Less: reclassification adjustment for instrument specific credit risk (gains) losses included in net income, net of income tax provision (benefit) of $(67), $78, $(166) and $78	199	(270)	493	(270)
Net change in unrealized instrument specific credit risk gains (losses), net of income tax provision (benefit) of $925, $8,797, $6,973 and $4,163	2,815	26,017	20,644	14,448
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $86, $(721), $0 and $513	251	251	0	1,499
Less: reclassification adjustment for cash flow hedges (gains) losses included in net income (loss), net of income tax provision (benefit) of $161, $0, $161 and $0	(470)	0	(470)	0
Net change in unrealized cash flow hedges gains (losses), net of income tax provision (benefit) of $(75), $(721), $(161) and $513	(219)	251	(470)	1,499
Net pension gains (losses) arising during the period, net of income tax provision (benefit) of $0, $0, $0 and $0	0	0	0	0
Reclassification adjustment for pension (gains) losses included in net income, net of income tax provision (benefit) of $(122), $(188), $(241) and $(339)	353	457	708	6,263
Net change in pension liability, net of income tax provision (benefit) of $122, $188, $241 and $339	353	457	708	6,263
Other comprehensive loss, net of income taxes	(581,443)	(42,344)	(531,110)	(30,167)
Comprehensive income	90,833	706,600	188,181	857,926
Comprehensive (income) loss attributable to the noncontrolling interests	191	(136)	(875)	1,208
Comprehensive (income) loss attributable to the redeemable noncontrolling interests	(427)	(22,108)	(289)	(36,904)
Preferred stock dividends	(1,276)	(1,171)	(2,552)	(2,343)
Comprehensive income attributable to Jefferies Financial Group Inc. common shareholders	$ 89,321	$ 683,185	$ 184,465	$ 819,887