Provision (Benefit) for Income Taxes (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of consolidated income tax provision (benefit)
Current income taxes	$ (1,144)	$ 1,616	$ (2,957)
Deferred income taxes	16,783	48,878	30,790
Income tax provision	$ 15,639	$ 50,494	$ 27,833