Consolidated Statements of Stockholders' Equity (Deficit) (USD $) In Thousands	Total	Common Stock Par Value $0.01 Per Share [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2011	$ 133,243	$ 271	$ 191,714	$ (2,557)	$ (56,185)
Balance, shares at Dec. 31, 2011		27,106
Issuance of common stock for exercise of stock options and vesting of RSUs, net of effect of early exercises and withholding tax	385	4	381
Issuance of common stock for exercise of stock options and vesting of RSUs, net of effect of early exercises and withholding tax, shares		389
Stock-based compensation expense	3,191		3,191
Foreign currency translation adjustment	47			47
Unrealized gain (loss) on investments	35			35
Net (loss) income	1,701				1,701
Balance at Mar. 31, 2012	138,602	275	195,286	(2,475)	(54,484)
Balance, shares at Mar. 31, 2012		27,495
Balance at Dec. 31, 2012	161,235	279	208,073	(3,008)	(44,109)
Balance, shares at Dec. 31, 2012		27,913
Issuance of common stock for exercise of stock options and vesting of RSUs, net of effect of early exercises and withholding tax	(938)	1	(939)
Issuance of common stock for exercise of stock options and vesting of RSUs, net of effect of early exercises and withholding tax, shares		111
Stock-based compensation expense	8,544		8,544
Tax windfall benefits on exercises of stock options	8,446		8,446
Foreign currency translation adjustment	(630)			(630)
Unrealized gain (loss) on investments	(3)			(3)
Net (loss) income	(2,317)				(2,317)
Balance at Mar. 31, 2013	$ 174,337	$ 280	$ 224,124	$ (3,641)	$ (46,426)
Balance, shares at Mar. 31, 2013		28,024