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]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Accumulated Deficit) [Member]
Beginning balance at Dec. 31, 2008	$ 193,423	$ 25	$ 233,246	$ (26,605)	$ 474	$ (13,717)
Beginning balance (in shares) at Dec. 31, 2008		23,516,198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuance of common stock under stock option plans, shares		321,886
Net issuance of common stock under stock option plans	2,005	1	1,968	36
Stock-based compensation	2,923		2,923
Components of comprehensive income:
Available-for-sale investments	(643)				(643)
Foreign exchange contracts	84				84
Change in minimum postretirement benefits obligation	47				47
Net income	2,129					2,129
Total comprehensive income	1,617
Ending balance at Dec. 31, 2009	199,968	26	238,137	(26,569)	(38)	(11,588)
Ending balance (in shares) at Dec. 31, 2009		23,838,084
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuance of common stock under stock option plans, shares		900,956
Net issuance of common stock under stock option plans	9,619	1	9,589	29
Stock-based compensation	4,839		4,839
Components of comprehensive income:
Available-for-sale investments	(68)				(68)
Change in minimum postretirement benefits obligation	(12)				(12)
Net income	16,781					16,781
Total comprehensive income	16,701
Ending balance at Dec. 31, 2010	231,127	27	252,565	(26,540)	(118)	5,193
Ending balance (in shares) at Dec. 31, 2010	24,739,040	24,739,040
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net issuance of common stock under stock option plans, shares		1,098,954
Net issuance of common stock under stock option plans	13,613		13,599	14
Stock-based compensation	9,017		9,017
Excess tax benefit related to stock options	3,023		3,023
Components of comprehensive income:
Available-for-sale investments	32				32
Change in minimum postretirement benefits obligation	(13)				(13)
Net income	39,230					39,230
Total comprehensive income	39,249
Ending balance at Dec. 31, 2011	$ 296,029	$ 27	$ 278,204	$ (26,526)	$ (99)	$ 44,423
Ending balance (in shares) at Dec. 31, 2011	25,837,994	25,837,994