Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 47,015	$ 139,149
Other comprehensive income (loss):
Net unrealized holding gains (losses) on investments arising during the period, net of income tax provision (benefit) of $107 and $(370)	317	(1,226)
Less: reclassification adjustment for net (gains) losses included in net income, net of income tax provision (benefit) of $(377) and $(5)	1,129	15
Net change in unrealized holding gains (losses) on investments, net of income tax provision (benefit) of $484 and $(365)	1,446	(1,211)
Net unrealized foreign exchange gains (losses) arising during the period, net of income tax provision (benefit) of $7,722 and $1,926	30,954	17,903
Less: reclassification adjustment for foreign exchange (gains) losses included in net income, net of income tax provision (benefit) of $0 and $0	0	0
Net change in unrealized foreign exchange gains (losses), net of income tax provision (benefit) of $7,722 and $1,926	30,954	17,903
Net unrealized gains (losses) on instrument specific credit risk arising during the period, net of income tax provision (benefit) of $5,949 and $(4,634)	17,535	(11,569)
Less: reclassification adjustment for instrument specific credit risk (gains) losses included in net income, net of income tax provision (benefit) of $(99) and $0	294	0
Net change in unrealized instrument specific credit risk gains (losses), net of income tax provision (benefit) of $6,048 and $(4,634)	17,829	(11,569)
Net unrealized gains (losses) on cash flow hedges arising during the period, net of income tax provision (benefit) of $(86) and $1,234	(251)	1,248
Less: reclassification adjustment for cash flow hedges (gains) losses included in net income (loss), net of income tax provision (benefit) of $0 and $0	0	0
Net change in unrealized cash flow hedges gains (losses), net of income tax provision (benefit) of $(86) and $1,234	(251)	1,248
Net pension gains (losses) arising during the period, net of income tax provision (benefit) of $0 and $0	0	0
Reclassification adjustment for pension (gains) losses included in net income, net of income tax provision (benefit) of $(119) and $(151)	355	5,806
Net change in pension liability, net of income tax provision (benefit) of $119 and $151	355	5,806
Other comprehensive income (loss), net of income taxes	50,333	12,177
Comprehensive income	97,348	151,326
Comprehensive (income) loss attributable to the noncontrolling interests	(1,066)	1,344
Comprehensive (income) loss attributable to the redeemable noncontrolling interests	138	(14,796)
Preferred stock dividends	(1,276)	(1,172)
Comprehensive income attributable to Jefferies Financial Group Inc. common shareholders	$ 95,144	$ 136,702