Investment Funds Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	21.00%
Investment funds	$ 1,140,218		$ 1,211,401
Income (Loss) from Investment Funds	50,838	$ 135,232
Alternative Investments, Fair Value Disclosure	353,700
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	534,854		466,703
Income (Loss) from Investment Funds	51,467	24,341
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	108,830		152,056
Income (Loss) from Investment Funds	(25,124)	18,136
Arbitrage
Schedule of Equity Method Investments [Line Items]
Investment funds	69,417		282,335
Income (Loss) from Investment Funds	(3,925)	15,270
Other
Schedule of Equity Method Investments [Line Items]
Investment funds	427,117		$ 310,307
Income (Loss) from Investment Funds	28,420	$ 77,485
Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 44,200

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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-Publisher FASB

-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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