Income Taxes (Income Tax Provision (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current income tax expense (benefit)
Federal	$ 57,720	$ (12,552)	$ 15,683
State	18,034	20,801	17,511
Total current income tax expense	75,754	8,249	33,194
Deferred income tax expense
Federal	239,862	329,715	143,381
State	15,881	12,748	16,968
Total deferred income tax expense	255,743	342,463	160,349
Total income tax expense	$ 331,497	$ 350,712	$ 193,543