Consolidated Statements of Stockholders Equity and Comprehensive Income (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]	Comprehensive Income [Member]
Balance at Dec. 31, 2008	$ 253,031	$ 1,478	$ 50,970	$ (1,623)	$ 201,304	$ 902
Balance, Shares at Dec. 31, 2008		14,731,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Shares		(589,000)
Treasury Stock, Value	(20,441)			(20,441)
Exercise of stock options, shares issued		50,000
Exercise of stock options, value	1,476	1	18	1,457
Employee stock purchase plan, shares issued	46,401	47,000
Employee stock purchase plan, value	1,271	2	543	726
Stock compensation	2,708		2,708
Research and development tax credit from stock options	118		118
Other comprehensive income (loss), net of tax:
Net Income	24,981				24,981		24,981
Foreign currency translation adjustment	285					285	285
Comprehensive Income							25,266
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)			(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	53,739	53,000
Employee stock purchase plan, value	1,576	2	296	1,278
Stock compensation	3,471		3,471
Other comprehensive income (loss), net of tax:
Net Income	29,923				29,923		29,923
Foreign currency translation adjustment	(2,251)					(2,251)	(2,251)
Comprehensive Income							27,672
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	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	(459,266)	459,000
Exercise of stock options, value	12,262	0	(3,753)	16,015
Employee stock purchase plan, shares issued	57,643	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
Other comprehensive income (loss), net of tax:
Net Income	44,669				44,669		44,669
Foreign currency translation adjustment	(2,170)					(2,170)	(2,170)
Comprehensive Income							42,499
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