Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Company's Stock Option Activity and Related Information

A summary of the Company’s stock option activity and related information is as follows:

				Options Outstanding
	Shares Available for Grant			Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining ContractualLife (Years)		Aggregate Intrinsic Value
											(In thousands)
Balance at December 31, 2017		969,783			8,592,747		$	3.69		7.4	$	47,864
Additional options authorized		2,706,158			—
Options granted		(182,244	)		182,244			8.16
Options exercised		—			(265,647	)		1.42
Options canceled		35,717			(35,717	)		5.62
Balance at March 31, 2018		3,529,414			8,473,627		$	3.85		7.4	$	22,906
Vested and exercisable at March 31, 2018					5,132,684		$	2.87		6.5	$	18,702
Vested and expected to vest at March 31, 2018					8,207,659		$	3.80		7.3	$	22,557

Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Option at Grant Date

The fair value of employee stock option was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions:  

	Three Months Ended March 31,
	2018		2017
Expected term (in years)		5.9		6.0
Expected volatility%	61.7%		67.1%
Risk-free interest rate%	2.6%		2.1%
Expected dividend yield%		0.0%		0.0%

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the Company’s condensed consolidated statements of operations is classified as follows (in thousands):

	Three Months Ended March 31,
	2018		2017
Research and development	$	203	$	165
Selling and marketing		127		51
General and administrative		860		553
Total stock-based compensation expense	$	1,190	$	769