Income Taxes Expense (Benefit) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current Income Tax Expense (Benefit) [Abstract]
Federal	$ 40,141	$ 38,333	$ 36,162
State	6,319	532	(322)
Total	46,460	38,865	35,840
Deferred Income Tax Expense (Benefit) [Abstract]
Federal	8,662	5,544	(20,432)
State	(4,284)	0	0
Total	4,378	5,544	(20,432)
Income Tax Expense (Benefit)	$ 50,838	$ 44,409	$ 15,408