Loans To And Investments In Associated Companies (Jefferies Finance) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Investments In Associated Companies [Line Items]
Investment banking	$ 404,062	$ 331,149	$ 655,057	$ 745,469
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions	1,300	4,200
Receivables	4,690,344		4,690,344		$ 3,934,825
Jefferies Finance [Member]
Investments In Associated Companies [Line Items]
Equity commitment	600,000		600,000
Funded Equity Commitments	486,500		$ 486,500
Investment commitment extension			1 year
Termination notice			60 days
Total line of credit facility commitment under joint venture	1,000,000		$ 1,000,000
Committed line of credit facility amount	700,000		700,000
Discretionary line of credit facility amount	300,000		$ 300,000
Extension period			1 year
Funded portion of line of credit commitment	0		$ 0		0
Line of credit facility commitment of Jefferies	350,000		350,000		350,000
Service fee income	7,100	7,000	34,900	28,700
Receivables	57,100		57,100		$ 41,500
Jefferies [Member]
Investments In Associated Companies [Line Items]
Investment banking	39,900	38,800	55,500	86,400
Origination fees	900	3,400	1,600	7,700
Service fee income	$ 3,100	$ 1,800	$ 3,100	$ 2,200