CONSOLIDATED STATEMENTS OF CHANGES IN MANDATORILY REDEEMABLE CONVERTIBLE PREFERRED STOCK, STOCKHOLDERS’ EQUITY (DEFICIT) AND COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Mandatorily Redeemable Convertible Preferred Stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2009	$ (37,664)	$ 70,502	$ 8	$ 0	$ 6,291	$ (1)	$ (43,962)
Beginning Balance, Shares at Dec. 31, 2009		13,142,000	7,509,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options	2,680				2,680
Issuance of common stock upon exercise of stock options (in shares)			663,000
Stock-based compensation expense	5,962				5,962
Stock compensation associated with outstanding repriced options	394				394
Purchase of treasury stock	(3,491)			(3,491)
Purchase of treasury stock (in shares)			(120,000)
Retirement of treasury stock	(2,596)			3,491	(895)		(2,596)
Retirement of treasury stock (in shares)			(250,000)
Accrued dividend on Series B mandatorily redeemable convertible preferred stock	(2,840)	2,840			(2,840)
Unrealized loss on available-for-sale securities	0
Excess tax benefit from stock-based compensation awards	319				319
Net (loss) income	3,803						3,803	3,803
Comprehensive (loss) income	3,803							3,803
Ending Balance at Dec. 31, 2010	(30,837)	73,342	8	0	11,911	(1)	(42,755)
Ending Balance, Shares at Dec. 31, 2010		13,142,000	7,802,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options	3,484		1		3,483
Issuance of common stock upon exercise of stock options (in shares)			1,084,000
Stock-based compensation expense	7,935				7,935
Stock compensation associated with outstanding repriced options	(463)				(463)
Retirement of treasury stock	0
Issuance of common stock in an initial public offering (“IPO”), net of discounts and issuance costs	62,163		4		62,159
Issuance of common stock in an initial public offering (“IPO”), net of discounts and issuance costs (in shares)			4,378,000
Accrued dividend on Series B mandatorily redeemable convertible preferred stock	(255)	255			(255)
Payment of accrued dividends on Series B mandatorily redeemable convertible preferred stock		(29,586)
Conversion of mandatorily redeemable convertible preferred stock to common stock in conjunction with the IPO	44,011	(44,011)	11		44,000
Conversion of mandatorily redeemable convertible preferred stock to common stock in conjunction with the IPO (in shares)		(13,142,000)	11,089,000
Conversion of preferred stock warrant to common stock warrant	140				140
Issuance of common stock upon release of restricted stock units (RSUs)			0
Unrealized loss on available-for-sale securities	(1)					(1)		(1)
Excess tax benefit from stock-based compensation awards	328				328
Net (loss) income	(3,573)						(3,573)	(3,573)
Comprehensive (loss) income	(3,574)							(3,574)
Ending Balance at Dec. 31, 2011	82,932	0	24	0	129,238	(2)	(46,328)
Ending Balance, Shares at Dec. 31, 2011		0	24,370,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options	1,711		1		1,710
Issuance of common stock upon exercise of stock options (in shares)			487,000
Stock-based compensation expense	4,402				4,402
Stock compensation associated with outstanding repriced options	17				17
Retirement of treasury stock	0
Issuance of common stock upon release of restricted stock units (RSUs)			45,000
Unrealized loss on available-for-sale securities	1					1		1
Excess tax benefit from stock-based compensation awards	(685)				(685)
Net (loss) income	(3,419)						(3,419)	(3,419)
Comprehensive (loss) income	(3,418)							(3,418)
Ending Balance at Dec. 31, 2012	$ 84,959	$ 0	$ 25	$ 0	$ 134,682	$ (1)	$ (49,747)
Ending Balance, Shares at Dec. 31, 2012		0	24,902,000