Consolidated Statements Of Stockholders' Equity And Comprehensive Income (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2008	$ 231	$ 98,521	$ 106,795	$ (2,121)	$ 12,720	$ 203,426
Balance, shares at Dec. 31, 2008	23,053
Net income			33,047		33,047	33,047
Other comprehensive gain (loss):
Unrealized gain (loss) on cash flow hedge, net of tax				875	875	875
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes, shares	306
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes	3	769				772
Stock-based compensation		4,384				4,384
Tax benefit from convertible notes interest expense		95				95
Tax benefit related to stock-based compensation		468				468
Tax benefit from repurchase of convertible notes		24				24
Balance at Dec. 31, 2009	234	104,261	139,842	(1,246)	33,922	243,091
Balance, shares at Dec. 31, 2009	23,359
Net income			49,052		49,052	49,052
Other comprehensive gain (loss):
Unrealized gain (loss) on cash flow hedge, net of tax				1,397	1,397	1,397
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes, shares	652
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes	6	(41)				(35)
Stock-based compensation		6,010				6,010
Settlement of call options and warrants associated with convertible notes, net		524				524
Reversal of previously established tax benefit related to convertible notes		(115)				(115)
Tax benefit related to stock-based compensation		2,773				2,773
Balance at Dec. 31, 2010	240	113,412	188,894	151	50,449	302,697
Balance, shares at Dec. 31, 2010	24,011
Net income			60,958		60,958	60,958
Other comprehensive gain (loss):
Unrealized gain (loss) on cash flow hedge, net of tax				(2,119)	(2,119)	(2,119)
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes, shares	509
Exercise of stock options and issuance of share-based awards, net of shares withheld for employee taxes	5	(2,405)				(2,400)
Stock-based compensation		7,709				7,709
Tax benefit related to stock-based compensation		4,690				4,690
Balance at Dec. 31, 2011	$ 245	$ 123,406	$ 249,852	$ (1,968)	$ 58,839	$ 371,535
Balance, shares at Dec. 31, 2011	24,520