Income Taxes (Schedule of Components of Income Tax Expense (Benefit)) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current:
Federal	$ 286	$ 4,115	$ 363
State	4,954	2,936	1,870
Current Income Tax Expense (Benefit)	5,240	7,051	2,233
Deferred:
Federal	80,083	(125,261)	47,709
State	2,798	(24,018)	4,026
Deferred Income Tax Expense (Benefit)	82,881	(149,279)	51,735
Total	$ 88,121	$ (142,228)	$ 53,968