Condensed Consolidated Statements of Comprehensive Operations (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 102,054	$ 85,367	$ 319,605	$ 410,699
Other comprehensive income, net of income tax:
Interest rate lock derivative contracts reclassified to income, net of tax of $11, $11, $30 and $32, respectively	17	17	54	52
Total other comprehensive income	17	17	54	52
Comprehensive income	$ 102,071	$ 85,384	$ 319,659	$ 410,751