CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
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
Unrealized (loss) gain on marketable securities	69				69
Foreign currency translation adjustments	(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
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
Unrealized (loss) gain on marketable securities	(20)				(20)
Foreign currency translation adjustments	(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
Increase (Decrease) in Stockholders' Equity
Stock-based award activity	(275)	8	(283)
Stock-based award activity (in shares)		786
Common stock repurchased and retired	(41,275)	(16)	(10,636)	(30,623)
Common stock repurchased and retired (in shares)	(1,651)	(1,651)
Common stock issued under employee stock purchase plan	6,661	3	6,658
Common stock issued under employee stock purchase plan (in shares)		325
Stock-based compensation	20,999		20,999
Tax shortfall from exercise of stock options	(672)		(672)
Tax benefit from exercise of stock options	7,785		7,785
Net income	30,415			30,415
Unrealized (loss) gain on marketable securities	4				4
Foreign currency translation adjustments	3,156				3,156
Balances at Dec. 31, 2012	$ 309,859	$ 505	$ 453,585	$ (154,261)	$ 10,030
Balances (in shares) at Dec. 31, 2012	50,457	50,457