Income Taxes (Provision) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current tax expense:
Federal	$ (3,400,000)	$ 77,800,000	$ 58,900,000
State	(1,200,000)	14,500,000	12,000,000
Total current tax expense	(4,600,000)	92,300,000	70,900,000
Deferred tax expense (benefit):
Federal	11,100,000	5,100,000	27,100,000
State	(2,200,000)	2,700,000	10,100,000
Total deferred tax expense (benefit)	8,924,000	7,771,000	37,164,000
Interest expense, gross of related tax effects	1,700,000	600,000	600,000
Total income tax provision	$ 5,969,000	$ 100,708,000	$ 108,727,000