Investments of Operating Entities and Consolidated Funds - Other Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Other investments	$ 80,452	$ 84,930
Operating Entities
Investment Holdings [Line Items]
Other investments	80,452	84,930
Operating Entities | Portfolio Funds
Investment Holdings [Line Items]
Other investments	57,549	55,898
Operating Entities | Real Estate Investments
Investment Holdings [Line Items]
Other investments	1,875	1,864
Operating Entities | Equity Method Investments
Investment Holdings [Line Items]
Other investments	20,368	26,462
Operating Entities | Lehman Claim
Investment Holdings [Line Items]
Other investments	660	706
Consolidated Funds
Investment Holdings [Line Items]
Other investments	193,497	204,205
Consolidated Funds | Portfolio Funds
Investment Holdings [Line Items]
Other investments	178,357	190,081
Consolidated Funds | Lehman Claim
Investment Holdings [Line Items]
Other investments	$ 15,140	$ 14,124