Loans To And Investments In Associated Companies (Jefferies Finance) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014
Investments In Associated Companies [Line Items]
Investment banking	$ 389,820	$ 465,192	$ 1,044,877	$ 1,210,661
Underwriting fees			1,300	4,200
Receivables	4,286,520		4,286,520			$ 3,934,825
Jefferies [Member]
Investments In Associated Companies [Line Items]
Investment banking	53,300	53,700	108,800	139,800
Origination fees	1,500	2,600	3,100	10,500
Service fee income	0	2,500	3,100	4,600
Jefferies Finance [Member]
Investments In Associated Companies [Line Items]
Equity commitment	600,000		600,000
Funded equity commitments	510,400		$ 510,400
Investment commitment extension			1 year
Termination notice			60 days
Total line of credit facility commitment under joint venture	500,000		$ 500,000		$ 1,000,000
Extension period			1 year
Funded portion of line of credit commitment	0		$ 0			0
Line of credit facility commitment of Jefferies	250,000		250,000			350,000
Service fee income	8,400	$ 6,500	43,300	$ 35,200
Receivables	$ 122,500		$ 122,500			$ 41,500