Consolidated Statements of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 409,597	$ 525,360	$ 573,333
Other comprehensive income, net of income tax:
Interest rate lock derivative contracts reclassified to income, net of tax of $40, $43 and $43, respectively	72	70	70
Total other comprehensive income	72	70	70
Comprehensive income	$ 409,669	$ 525,430	$ 573,403