Condensed Consolidated Statements of Comprehensive Operations (Unaudited) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements of Comprehensive Operations (unaudited) [Abstract]
Net income	$ 85,367,000	$ 275,670,000	$ 410,699,000	$ 520,726,000
Other comprehensive income (loss), net of income tax:
Net unrealized loss on available-for-sale securities, net of tax of $2,420 and $4,244, respectively	0	(3,949,000)	0	(6,925,000)
Interest rate lock derivative contracts reclassified to income, net of tax of $11, $11, $32 and $32, respectively	17,000	17,000	52,000	52,000
Total other comprehensive income (loss)	17,000	(3,932,000)	52,000	(6,873,000)
Comprehensive income	$ 85,384,000	$ 271,738,000	$ 410,751,000	$ 513,853,000