Stock‑Based Compensation (Tables)

9 Months Ended

Sep. 30, 2015

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, 2014	294	8,463	$	2.28	8.83
Additional shares authorized	4,985	-
Options granted	(1,736)	1,736		10.19
Options exercised	-	(323)		1.76
Options forfeited	477	(477)		3.49
Balance at September 30, 2015	4,020	9,399		3.25	8.48	65,607
Exercisable at September 30, 2015		5,727		1.70	6.00	51,081
Vested and expected to vest at September 30, 2015		8,473		3.39	7.71	60,979

Summary of stock-based compensation expenses

	Three months ended  September 30,
	2015						2014
	Employee		Non‑Employee		Total		Employee		Non‑Employee		Total
	(in thousands)
Cost of revenues	$	400	$	10	$	410	$	102	$	12	$	114
Research and development		266		2		268		244		7		251
Selling, general and administrative		1,491		(3)		1,488		639		61		700
Total	$	2,157	$	9	$	2,166	$	985	$	80	$	1,065

	Nine months ended September 30,
	2015						2014
	Employee		Non‑Employee		Total		Employee		Non‑Employee		Total
	(in thousands)
Cost of revenues	$	549	$	217	$	766	$	199	$	16	$	215
Research and development		824		24		848		1,388		14		1,402
Selling, general and administrative		3,202		90		3,292		2,401		74		2,475
Total	$	4,575	$	331	$	4,906	$	3,988	$	104	$	4,092

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

	Three months ended										Nine months ended
	September 30,										September 30,
	2015					2014					2015					2014
Expected term	5.7		—	6.1		4.91		—	5.85		5.6		—	6.5		4.9		—	6.3
Expected volatility	69.7	%	—	71.9	%	73.3	%	—	82.8	%	69.7	%	—	78.8	%	73.1	%	—	87.3	%
Expected dividend rate				0	%				0	%				0	%				0	%
Risk‑free interest rate	1.65	%	—	1.80	%	1.83	%	—	2.04	%	1.56	%	—	1.96	%	1.65	%	—	2.09	%