Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

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

Employee stock-based compensation

Stock-based compensation for employee option awards is included in the condensed consolidated statements of operations as follows:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2015		2014		2015		2014
	(in thousands)
Cost of revenues	$	333	$	175	$	1,005	$	482
Research and development	1,294		599		3,584		1,544
Sales and marketing	1,015		561		2,806		1,839
General and administrative	1,674		1,050		4,612		2,815
Total employee stock-based compensation	$	4,316	$	2,385	$	12,007	$	6,680

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,
	2015	2014	2015	2014
Expected term (in years)	4.9 to 5.9	5.3 to 5.9	4.9 to 5.9	5.3 to 5.9
Volatility	45% to 46%	48% to 50%	45% to 48%	48% to 52%
Risk-free interest rate	1.62%	1.67%	1.3% to 1.65%	1.52% to 1.67%
Dividend yield	—%	—%	—%	—%

Stock option activity

A 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)
December 31, 2014	7,605,407		$	12.93	6.5	$	188,743
Granted	1,113,950		41.17
Exercised	(567,227	)	11.63
Canceled	(560,025	)	26.69
September 30, 2015	7,592,105		16.16		6.1	107,966
Vested and expected to vest - September 30, 2015	7,130,958		15.00		5.9	106,964
Exercisable - September 30, 2015	5,073,823		8.79		4.9	99,803