Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based employee compensation

tock-based compensation is included in the condensed consolidated statements of operations as follows:

	Three Months Ended				Nine months ended
	September 30,				September 30,
	2013		2012		2013		2012
	(in thousands)
Cost of revenues	$	103	$	68	$	297	$	191
Research and development	253		167		687		461
Sales and marketing	363		306		804		746
General and administrative	507		244		1,299		723
Total stock-based employee compensation	$	1,226	$	785	$	3,087	$	2,121

Fair value assumptions of options granted to employees

The fair value of each option granted to employees is estimated on the date of grant using the Black-Scholes option-pricing model based on the following assumptions:

	Three Months Ended		Nine months ended
	September 30,		September 30,
	2013	2012	2013	2012
Expected term (in years)	5.4 to 6.1	5.3 to 6.0	5.4 to 6.1	5.3 to 6.0
Volatility	52% to 53%	53%	52% to 53%	53%
Risk-free interest rate	1.4% to 1.5%	0.6% to 0.7%	0.7% to 1.5%	0.6% to 0.8%
Dividend yield	—	—	—	—

Stock option activity

summary of the Company’s stock option activity is as follows:

	Outstanding Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
Balance as of December 31, 2012	6,513,508		$	4.39	6.6	$	67,711
Granted	1,412,325		13.34
Exercised	(816,166	)	4.13
Canceled	(339,713	)	9.07
Balance as of September 30, 2013	6,769,954		6.06		6.5	103,805
Vested and expected to vest - September 30, 2013	6,109,405		5.53		6.3	96,911
Exercisable - September 30, 2013	5,406,675		4.19		5.7	82,897