Investments of Operating Entities and Consolidated Funds - Other Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investment Holdings [Line Items]
Other investments	$ 84,930	$ 59,943
Operating Entities
Investment Holdings [Line Items]
Other investments	84,930	59,943
Operating Entities | Portfolio Funds
Investment Holdings [Line Items]
Other investments	55,898	40,350
Operating Entities | Real Estate Investments
Investment Holdings [Line Items]
Other investments	1,864	2,353
Operating Entities | Equity Method Investments [Member]
Investment Holdings [Line Items]
Other investments	26,462	16,687
Operating Entities | Lehman Claim
Investment Holdings [Line Items]
Other investments	706	553
Consolidated Funds
Investment Holdings [Line Items]
Other investments	204,205	228,820
Consolidated Funds | Portfolio Funds
Investment Holdings [Line Items]
Other investments	190,081	221,480
Consolidated Funds | Lehman Claim
Investment Holdings [Line Items]
Other investments	$ 14,124	$ 7,340