Investment Funds Investment Funds (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	28.10%
Investment funds	$ 1,214,272,000us-gaap_EquityMethodInvestments		$ 1,211,401,000us-gaap_EquityMethodInvestments
Income (Loss) from Investment Funds	6,061,000	53,799,000
Alternative Investments, Fair Value Disclosure	385,000,000
Real estate
Schedule of Equity Method Investments [Line Items]
Investment funds	481,822,000		466,703,000
Income (Loss) from Investment Funds	26,012,000	12,295,000
Energy
Schedule of Equity Method Investments [Line Items]
Investment funds	119,813,000		152,056,000
Income (Loss) from Investment Funds	(21,868,000)	8,601,000
Arbitrage
Schedule of Equity Method Investments [Line Items]
Investment funds	281,462,000		282,335,000
Income (Loss) from Investment Funds	(873,000)	5,107,000
Other
Schedule of Equity Method Investments [Line Items]
Investment funds	331,175,000		310,307,000
Income (Loss) from Investment Funds	2,790,000	27,796,000
Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Investment funds	$ 46,000,000

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

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+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Fair value portion of investments accounted under the equity method.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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

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