Income Taxes (Schedule of Components of Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current:
Federal	$ 4,115	$ 363	$ 3,148
State	2,936	1,870	782
Current Income Tax Expense (Benefit)	7,051	2,233	3,930
Deferred:
Federal	(125,261)	47,709	20,885
State	(24,018)	4,026	(4,151)
Deferred Income Tax Expense (Benefit)	(149,279)	51,735	16,734
Total	$ (142,228)	$ 53,968	$ 20,664