Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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	3,743	9,316	$	3.96	8.31	$	63,713
Additional shares authorized	2,014	—
Options granted	(2,558)	2,558	$	10.23
Options exercised	—	(1,915)	$	1.88
Options forfeited	916	(916)	$	8.28
Balance at December 31, 2016	4,115	9,043	$	5.72	7.55	$	55,396
Exercisable at December 31, 2016		5,054	$	3.10	6.51	$	43,938
Vested and expected to vest at December 31, 2016		9,039	$	5.72	7.55	$	55,386

Restricted stock units

			Weighted-Average Grant Date
	Shares		Fair Value
Balance at December 31, 2015		—	$	—
Granted		212	$	9.76
Vested		(40)	$	9.59
Canceled/forfeited		(13)	$	9.81
Balance at December 31, 2016		159	$	9.80

Summary of stock-based compensation expenses

	Year ended December 31,
	2016						2015						2014
	Employee		Non-Employee		Total		Employee		Non-Employee		Total		Employee		Non-Employee		Total
	(in thousands)
Cost of revenues	$	651	$	(10)	$	641	$	351	$	241	$	592	$	262	$	29	$	291
Research and development		2,829		24		2,853		1,566		9		1,575		1,563		30		1,593
Selling, general and administrative		6,837		270		7,107		4,993		166		5,159		3,180		93		3,273
Total	$	10,317	$	284	$	10,601	$	6,910	$	416	$	7,326		5,005	$	152	$	5,157

Employee stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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

	Year ended December 31,
	2016					2015					2014
Expected term	5.1		—	5.2		5.6		—	10.0		4.9 — 7.1
Expected volatility	62.2	%	—	72.5	%	69.7	%	—	78.8	%	73.4	%	—	87.0	%
Expected dividend rate				0	%				0	%				0	%
Risk-free interest rate	0.97	%	—	1.92	%	1.56	%	—	2.32	%	1.65	%	—	2.04	%

Non-employee stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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

	Year ended December 31,
	2016					2015					2014
Expected term	2.7		—	3.2		4.9		—	9.8		4.4  — 10.0
Expected volatility	50.9	%	—	72.6	%	70.2	%	—	75.4	%	71.9	%	—	80.2	%
Expected dividend rate				0	%				0	%				0	%
Risk-free interest rate	0.68	%	—	1.38	%	1.74	%	—	2.24	%	1.41	%	—	2.61	%