Investment Funds Investment Funds (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 956,701		$ 1,067,495
Income (Loss) from Investment Funds	53,799	10,934
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	273,748		378,435
Income (Loss) from Investment Funds	12,295	(2,001)
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	159,612		155,026
Income (Loss) from Investment Funds	8,601	9,466
Arbitrage
Schedule of Equity Method Investments [Line Items]
Investment funds	276,682		271,575
Income (Loss) from Investment Funds	5,107	(458)
Other
Schedule of Equity Method Investments [Line Items]
Investment funds	246,659		262,459
Income (Loss) from Investment Funds	$ 27,796	$ 3,927