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, 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)
Exercise of stock options, shares issued		459,000
Employee stock purchase plan, shares issued		58,000
Treasury Stock, Value	(11,956)	0	0	(11,956)
Exercise of stock options, value	12,262	0	(3,753)	16,015
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares issued		526,000
Employee stock purchase plan, shares issued		61,000
Exercise of stock options, value	19,411	0	1,348	18,063
Employee stock purchase plan, value	2,220	0	63	2,157
Stock compensation	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	14,488,000	14,458,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options, shares issued		733,000
Treasury stock shares acquired in lieu of cash payment on exercise of options or payment of tax obligations		(140,000)
Employee stock purchase plan, shares issued		51,000
Exercise of stock options, value	24,970	24	2,030	22,916
Treasury stock withheld in lieu of cash payment on exercise of options or payment of tax obligations				(9,711)
Common stock acquired in lieu of cash payment on option exercises	(3,033)		6,678
Employee stock purchase plan, value	2,457		583	1,874
Stock compensation	5,434		5,434
Foreign Currency Translation Adjustment	3,622					3,622
Net Income	40,418				40,418
Balance at Dec. 31, 2013	$ 464,725	$ 1,510	$ 78,495	$ (49)	$ 382,576	$ 2,193
Balance, Shares at Dec. 31, 2013	15,102,000	15,102,000