Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 62,455	$ 55,213	$ 31,282
Other comprehensive income (loss) before tax and net of reclassification adjustments:
Change in fair value of interest rate swaps	317	(1,868)	(364)
Unrealized loss on available-for-sale securities		(947)
Other comprehensive income (loss), before tax	317	(2,815)	(364)
Income tax expense (benefit) related to components of other comprehensive income	124	(1,088)	(142)
Other comprehensive income (loss), net of tax	193	(1,727)	(222)
Comprehensive income	$ 62,648	$ 53,486	$ 31,060