Investments In Associated Companies (Schedule Of Income (Losses) Related To Associated Companies) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	$ 401,908	$ (44,172)
Income tax provision (benefit)	139,369	(16,124)
Income (losses) related to associated companies, net of taxes	262,539	(28,048)
Jefferies Group, Inc. [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	299,601	(79,702)
Mueller [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	74,315
JHYH [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	9,694	14,928
Berkadia [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	11,820	14,659
Garcadia [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	8,094	4,295
Linkem [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	(4,190)
HomeFed Corporation [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	(115)	(18)
Brooklyn Renaissance Plaza [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	441	643
Associated Companies Other [Member]
Investments In Associated Companies [Line Items]
Income (losses) related to associated companies before income taxes	$ 2,248	$ 1,023