Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (USD $) In Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Earnings	Accumulated Other Comprehensive (Loss) Income
Balance at Dec. 31, 2011	$ 371,535	$ 245	$ 123,406	$ 249,852	$ (1,968)
Balance, Shares at Dec. 31, 2011		24,520
Net income	49,310			49,310
Unrealized gain on derivative instruments, net of tax	733				733
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes	(613)	5	(618)
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes, Shares		482
Stock-based compensation	6,710		6,710
Tax benefit related to stock-based compensation	3,507		3,507
Balance at Sep. 30, 2012	$ 431,182	$ 250	$ 133,005	$ 299,162	$ (1,235)
Balance, Shares at Sep. 30, 2012		25,002