Provision (Benefit) for Income Taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of consolidated income tax provision (benefit)
Current income taxes	$ 1,616	$ (2,957)	$ (10,792)
Deferred income taxes	48,995	32,881	(13,377)
Income tax provision	$ 50,494	$ 27,833	$ (25,541)