Consolidated Statements Of Stockholders' Equity (USD $) In Thousands	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Notes For Preferred Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2008	$ 212,864	$ 65	$ 92,564	$ 162,464	$ (175,220)	$ (195)	$ (19,278)	$ 273,264
Net income				89,052				89,052
Fair value of interest rate swaps, net of tax							2,731	2,731
Other comprehensive income from currency exchange, net of tax							4,374	4,374
Total comprehensive income								96,157
Payment of note for preferred stock						195		195
Issuance of common stock		1	2,930					2,931
Issuance of preferred stock	102,000							102,000
Issuance of preferred stock			(498)					(498)
Accretion of convertible preferred stock	15,790			(15,790)
Balance at Dec. 31, 2009	330,654	66	94,996	235,726	(175,220)		(12,173)	474,049
Net income				107,896				107,896
Fair value of interest rate swaps, net of tax							3,957	3,957
Other comprehensive income from currency exchange, net of tax							115	115
Total comprehensive income								111,968
Payment of dividends on convertible preferred stock	(7,635)							(7,635)
Conversion of convertible preferred stock to common stock in connection with initial public offering	(323,019)	45	279,433	43,541
Issuance of common stock		1	47,562					47,563
Balance at Dec. 31, 2010		112	421,991	387,163	(175,220)		(8,101)	625,945
Net income				147,335				147,335
Other comprehensive income from currency exchange, net of tax							(5,615)	(5,615)
Total comprehensive income								141,720
Repurchase of common stock					(443)			(443)
Issuance of common stock		2	44,212					44,214
Balance at Dec. 31, 2011		$ 114	$ 466,203	$ 534,498	$ (175,663)		$ (13,716)	$ 811,436