Investment Funds Investment Funds (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	25.80%
Investment funds	$ 1,123,829		$ 1,211,401
Income (Loss) from Investment Funds	27,912	$ 76,155
Alternative Investments, Fair Value Disclosure	457,000
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	506,774		466,703
Income (Loss) from Investment Funds	42,337	16,482
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	113,779		152,056
Income (Loss) from Investment Funds	(27,484)	12,596
Arbitrage
Schedule of Equity Method Investments [Line Items]
Investment funds	72,752		282,335
Income (Loss) from Investment Funds	(590)	8,231
Other funds
Schedule of Equity Method Investments [Line Items]
Investment funds	430,524		$ 310,307
Income (Loss) from Investment Funds	13,649	$ 38,846
Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 45,000

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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-Name Accounting Standards Codification

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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