Investments in Affiliates (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Investments in affiliates	$ 1,126,875		$ 1,052,729
Investment fund affiliates
Schedule of Equity Method Investments [Line Items]
Investments in affiliates	845,197	[1]	768,851	[1]
Operating affiliates
Schedule of Equity Method Investments [Line Items]
Investments in affiliates	$ 281,678		$ 283,878

[1] The Company generally records its alternative fund affiliates on a one month lag and its private investments fund affiliates on a three month lag.