Condensed Consolidated Statements Stockholders' Equity (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance, Value at Dec. 31, 2011	$ 316,115	$ 3,638	$ (76)	$ 179,518	$ 137,559	$ (4,524)
Beginning Balance, Issued Shares at Dec. 31, 2011	36,418,385	36,418,385
Beginning Balance, Treasury Shares at Dec. 31, 2011			(40,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	51,824				51,824
Cumulative translation adjustment	(2,182)					(2,182)
Repurchase and retirement of common stock, Shares		(787,518)
Repurchase and retirement of common stock, Value	(15,150)	(79)		(15,071)
Vesting of restricted stock, Shares		77,159
Vesting of restricted stock, Value	0	6		(6)
Exercise of stock options, Shares		1,209,542
Exercise of stock options, Value	739	122		617
Share based compensation	1,567			1,567
Share subscribed for business acquisition, Shares		296,560
Share subscribed for business acquisition, Value	5,000	30		4,970
Tax benefit related to share-based compensation	73			73
Dividends paid	(5,161)				(5,161)
Ending Balance, Value at Sep. 30, 2012	$ 352,825	$ 3,717	$ (76)	$ 171,668	$ 184,222	$ (6,706)
Ending Balance, Issued Shares at Sep. 30, 2012	37,214,128	37,214,128
Ending Balance, Treasury Shares at Sep. 30, 2012			(40,509)