Consolidated Statements of Stockholders Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2009	$ 263,429	$ 1,481	$ 54,357	$ (19,881)	$ 226,285	$ 1,187
Balance, Shares at Dec. 31, 2009		14,239,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares		(821,000)
Treasury Stock, Value	(28,648)	0	0	(28,648)
Exercise of stock options, shares issued		188,000
Exercise of stock options, value	4,204	3	(1,622)	5,823
Employee stock purchase plan, shares issued		53,000
Employee stock purchase plan, value	1,576	2	296	1,278
Stock compensation	3,471		3,471
Foreign Currency Translation Adjustment	(2,251)					(2,251)
Net Income	29,923				29,923
Balance at Dec. 31, 2010	271,704	1,486	56,502	(41,428)	256,208	(1,064)
Balance, Shares at Dec. 31, 2010		13,659,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares		(305,000)
Treasury Stock, Value	(11,956)			(11,956)
Exercise of stock options, shares issued		459,000
Exercise of stock options, value	12,262	0	(3,753)	16,015
Employee stock purchase plan, shares issued		58,000
Employee stock purchase plan, value	1,828	0	(193)	2,021
Stock compensation	4,016		4,016
Research and development tax credit from stock options	224		224
Foreign Currency Translation Adjustment	(2,170)					(2,170)
Net Income	44,669				44,669
Balance at Dec. 31, 2011	320,577	1,486	56,796	(35,348)	300,877	(3,234)
Balance, Shares at Dec. 31, 2011	13,871,000	13,871,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares issued		526,000
Exercise of stock options, value	19,411	0	1,348	18,063
Employee stock purchase plan, shares issued		61,000
Employee stock purchase plan, value	2,220		63	2,157
Stock compensation	5,563		5,563
Foreign Currency Translation Adjustment	1,805					1,805
Net Income	41,281				41,281
Balance at Dec. 31, 2012	$ 390,857	$ 1,486	$ 63,770	$ (15,128)	$ 342,158	$ (1,429)
Balance, Shares at Dec. 31, 2012	14,458,000	14,458,000