Variable Interest Entities (Assets And Liabilities Of Consolidated VIEs) (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Variable Interest Entity [Line Items]
Cash		$ 4,895,788	$ 5,275,480	$ 5,016,932
Financial instruments owned		19,577,665	16,799,237
Securities purchased under agreement to resell		3,659,059	3,689,559
Receivables		5,864,815	5,419,015
Other		1,506,986	1,661,777
Total assets	[1]	48,948,669	47,169,108
Other secured financings		1,440,678	1,029,485
Total liabilities	[1]	38,155,533	36,478,536
Noncontrolling interests		25,566	33,022
Jefferies Group
Variable Interest Entity [Line Items]
Secured financings eliminated in consolidation		37,700	44,100
Consolidation, Eliminations
Variable Interest Entity [Line Items]
Intercompany payables		31,100	32,000
Securitization Vehicles
Variable Interest Entity [Line Items]
Cash		0	11,700
Financial instruments owned		0	37,600
Securities purchased under agreement to resell		1,043,400	729,300
Receivables		453,200	318,100
Other		25,800	15,500
Total assets		1,522,400	1,112,200
Other secured financings		1,478,300	1,073,500
Other		44,100	38,300
Total liabilities		$ 1,522,400	$ 1,111,800

[1] Total assets include assets related to variable interest entities of $479.0 million and $382.9 million at September 30, 2018 and December 31, 2017, respectively, and Total liabilities include liabilities related to variable interest entities of $1,441.9 million and $1,031.0 million at September 30, 2018 and December 31, 2017, respectively. See Note 8 for additional information related to variable interest entities.