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 Income
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	33,752				33,752
Cumulative translation adjustment	(3,378)					(3,378)
Repurchase and retirement of common stock, Shares		(506,700)
Repurchase and retirement of common stock, Value	(9,396)	(51)		(9,345)
Vesting of restricted stock, Shares		65,390
Vesting of restricted stock, Value	1	14		(13)
Exercise of stock options, Shares		1,158,000
Exercise of stock options, Value	714	117		597
Deferred compensation and amortization related to options and restricted stock	1,059			1,059
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	50			50
Dividends paid	(3,296)				(3,296)
Ending Balance, Value at Jun. 30, 2012	$ 340,621	$ 3,748	$ (76)	$ 176,836	$ 168,015	$ (7,902)
Ending Balance, Issued Shares at Jun. 30, 2012	37,431,635	37,431,635
Ending Balance, Treasury Shares at Jun. 30, 2012			(40,509)