Other Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Comprehensive Income (Loss) [Abstract]
Net (loss) income	$ 28,620,000	$ 16,525,000	$ 348,000	$ 29,699,000	$ (50,831,000)	$ 14,331,000	$ 14,041,000	$ 19,671,000	$ 75,192,000	$ (2,788,000)	$ 31,409,000
Interest rate swap, net of tax									0	20,529,000	8,507,000
Temporary decline in available-for-sale securities									0	0	90,000
Comprehensive income (loss)									75,180,000	17,741,000	40,006,000
Income Tax Benefit Allocated to Interest Rate Swap										9,500,000	5,400,000
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 300,000				$ (282,000)				$ 300,000	$ (282,000)