Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

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

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



	Three months ended				Six months ended
	June 30,				June 30,
	2015		2014		2015		2014
	(in thousands)
Cost of revenues	$	344	$	158	$	672	$	307
Research and development	1,138		510		2,290		945
Sales and marketing	980		705		1,791		1,278
General and administrative	1,467		992		2,938		1,765
Total employee stock-based compensation	$	3,929	$	2,365	$	7,691	$	4,295

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		Six months ended
	June 30,		June 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	46%	49% to 50%	46% to 48%	49% to 52%
Risk-free interest rate	1.5% to 1.65%	1.65% to 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	584,700		44.70
Exercised	(484,876	)	11.44
Canceled	(348,274	)	27.31
June 30, 2015	7,356,957		14.88		6.2	189,858
Vested and expected to vest - June 30, 2015	6,916,031		13.85		6.0	184,876
Exercisable - June 30, 2015	4,813,369		7.68		4.9	157,244