Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock at Cost
Balance at Dec. 31, 2009	$ 68,509	$ 2	$ 246,383	$ 19	$ (177,895)
Balance (in shares) at Dec. 31, 2009		28,681,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options for cash	2,983	1	2,982
Issuance of common stock upon exercise of stock options for cash (in shares)		327,000
Stock-based compensation expense related to employee stock options	10,344		10,344
Stock-based compensation expense related to consultant stock options	15		15
Net income	4,288				4,288
Unrealized gain (loss) on investments, net of tax	(29)			(29)
Balance at Dec. 31, 2010	86,110	3	259,724	(10)	(173,607)
Balance (in shares) at Dec. 31, 2010		29,008,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options for cash	9,558		9,558
Issuance of common stock upon exercise of stock options for cash (in shares)		748,000
Issuance of restricted stock to directors in lieu of fees	130		130
Issuance of restricted stock to directors in lieu of fees (in shares)		5,000
Stock-based compensation expense related to employee stock options	11,735		11,735
Net income	7,846				7,846
Unrealized gain (loss) on investments, net of tax	(20)			(20)
Balance at Dec. 31, 2011	115,359	3	281,147	(30)	(165,761)
Balance (in shares) at Dec. 31, 2011	29,761,022	29,761,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options for cash and vesting of restricted stock units	14,086		14,086
Issuance of common stock upon exercise of stock options for cash and vesting of restricted stock units (in shares)		1,025,000
Issuance of common stock upon settlement of employee stock purchase plan	3,406		3,406
Issuance of common stock upon settlement of employee stock purchase plan (in shares)		146,000
Issuance of restricted stock to directors in lieu of fees	172		172
Issuance of restricted stock to directors in lieu of fees (in shares)		6,000
Stock-based compensation expense related to employee stock options	15,104		15,104
Repurchase of common stock	(30,095)					(30,095)
Repurchase of common stock (in shares)	(984,074)	(984,000)
Net income	8,249				8,249
Unrealized gain (loss) on investments, net of tax	45			45
Balance at Dec. 31, 2012	$ 126,326	$ 3	$ 313,915	$ 15	$ (157,512)	$ (30,095)
Balance (in shares) at Dec. 31, 2012	29,953,815	29,954,000