Intangible Assets, Net (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Summary of intangible assets
Investment contracts	$ 197,143	$ 269,489
Accumulated amortization	(179,372)	(249,809)
Definite-lived intangible assets, net	17,771	19,680
Indefinite-lived intangible assets	32,416	32,416
Total intangible assets, net	$ 50,187	$ 52,096	$ 51,078	$ 52,977