CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Comprehensive Income	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Balances at Dec. 31, 2008	$ 195,823		$ 514	$ 365,094	$ (176,484)	$ 6,699
Balances (in shares) at Dec. 31, 2008			51,457
Increase (Decrease) in Stockholders' Equity
Stock-based award activity	6,441		11	6,430
Stock-based award activity (in shares)			1,104
Common stock repurchased and retired	(14,578)		(14)	(8,581)	(5,983)
Common stock repurchased and retired (in shares)	(1,380)		(1,380)
Common stock issued under employee stock purchase plan	5,621		6	5,615
Common stock issued under employee stock purchase plan (in shares)			553
Stock-based compensation	18,648			18,648
Tax shortfall from exercise of stock options	(853)			(853)
Other	12			12
Net income	36,883	36,883			36,883
Unrealized gain (loss) on marketable securities (net of applicable taxes of $(5), $48 and $(43), respectively)	(62)	(62)				(62)
Foreign currency translation adjustments	4,099	4,099				4,099
Balances at Dec. 31, 2009	252,034		517	386,365	(145,584)	10,736
Balances (in shares) at Dec. 31, 2009			51,734
Increase (Decrease) in Stockholders' Equity
Stock-based award activity	8,553		16	8,537
Stock-based award activity (in shares)			1,572
Common stock repurchased and retired	(35,881)		(16)	(10,409)	(25,456)
Common stock repurchased and retired (in shares)	(1,670)		(1,670)
Common stock issued under employee stock purchase plan	5,793		3	5,790
Common stock issued under employee stock purchase plan (in shares)			338
Stock-based compensation	18,524			18,524
Tax shortfall from exercise of stock options	(1,073)			(1,073)
Tax benefit from exercise of stock options	3,878			3,878
Other	(12)			(12)
Net income	24,153	24,153			24,153
Unrealized gain (loss) on marketable securities (net of applicable taxes of $(5), $48 and $(43), respectively)	69	69				69
Foreign currency translation adjustments	(2,190)	(2,190)				(2,190)
Balances at Dec. 31, 2010	273,848		520	411,600	(146,887)	8,615
Balances (in shares) at Dec. 31, 2010	51,974		51,974
Increase (Decrease) in Stockholders' Equity
Stock-based award activity	1,414		10	1,404
Stock-based award activity (in shares)			993
Common stock repurchased and retired	(51,582)		(23)	(14,223)	(37,336)
Common stock repurchased and retired (in shares)	(2,243)		(2,243)
Common stock issued under employee stock purchase plan	6,158		3	6,155
Common stock issued under employee stock purchase plan (in shares)			273
Stock-based compensation	19,371			19,371
Tax shortfall from exercise of stock options	(1,628)			(1,628)
Tax benefit from exercise of stock options	7,055			7,055
Net income	30,170	30,170			30,170
Unrealized gain (loss) on marketable securities (net of applicable taxes of $(5), $48 and $(43), respectively)	(20)	(20)				(20)
Foreign currency translation adjustments	(1,725)	(1,725)				(1,725)
Balances at Dec. 31, 2011	$ 283,061		$ 510	$ 429,734	$ (154,053)	$ 6,870
Balances (in shares) at Dec. 31, 2011	50,997		50,997