Stock‑Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Stock-Based Compensation

Summary of stock option activity

	Outstanding Options
					Weighted-
			Weighted-		Average
	Shares		Average		Remaining	Aggregate
	Available for	Number of	Exercise		Contractual	Intrinsic
(in thousands, except for contractual life and exercise price)	Grant	Shares	Price		Life	Value
					(In years)
Balance at December 31, 2015	3,734	9,324	$	3.96
Additional shares authorized	2,014	—
Options granted	(122)	122	$	7.79
Options exercised	—	(667)	$	1.96
Options forfeited/cancelled	384	(384)	$	5.29
Balance at March 31, 2016	6,010	8,395	$	4.11	7.38	$	48,499
Exercisable at March 31, 2016		5,241	$	2.12	6.50	$	38,941
Vested and expected to vest at March 31, 2016		8,021	$	3.93	7.31	$	47,533

Summary of stock-based compensation expenses

	Three months ended  March 31,
	2016						2015
	Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	158	$	(25)	$	133	$	62	$	22	$	83
Research and development		606		(1)		605		249		12		261
Selling, general and administrative		1,461		197		1,658		784		19		803
Total	$	2,225	$	171	$	2,396	$	1,095	$	52	$	1,147

Schedule of assumptions used in valuation of fair value of employee stock options

	Three months ended  March 31,
	2016					2015
Expected term	5.1		—	5.2		5.6		—	5.7
Expected volatility	70.6	%	—	71.0	%	72.6	%	—	73.0	%
Expected dividend rate				0	%				0	%
Risk-free interest rate	1.25	%	—	1.51	%	1.56	%	—	1.58	%