Loans To And Investments In Associated Companies (Jefferies Finance) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Investments In Associated Companies [Line Items]
Investment banking	$ 230,930	$ 250,995
Commissions	155,824	166,922
Receivables	4,178,419		$ 3,830,967
Jefferies [Member]
Investments In Associated Companies [Line Items]
Investment banking	19,400	15,600
Origination fees		700
Jefferies Finance [Member]
Investments In Associated Companies [Line Items]
Equity commitment	600,000
Funded equity commitments	$ 474,400
Investment commitment extension	1 year
Termination notice	60 days
Total line of credit facility commitment under joint venture	$ 500,000		500,000
Extension period	1 year
Funded portion of line of credit commitment	$ 0		19,300
Line of credit facility commitment of Jefferies	250,000		250,000
Commissions	1,400
Service fee income	21,100	$ 27,800
Receivables	$ 6,000		$ 7,800