Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

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 Contractual Life (Years)		Aggregate Intrinsic Value
											(In thousands)
Balance at December 31, 2018		1,908,626			11,603,708		$	6.64		7.6	$	10,151
Additional options authorized		3,853,280
Options granted		(1,872,022	)		1,872,022			8.28
Options exercised		-			(588,120	)		4.90
Options canceled		79,293			(79,293	)		7.49
RSUs granted		(651,392	)
Balance at March 31, 2019		3,317,785			12,808,317		$	6.95		7.9	$	16,290
Vested and exercisable at March 31, 2019					4,071,182		$	4.32		5.9	$	12,759
Vested and expected to vest at March 31, 2019					12,181,953		$	6.89		7.9	$	16,094

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 is estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions:  

	Three Months Ended March 31,
	2019		2018
Expected term (in years)		6.0		5.9
Expected volatility%	60.4%		61.7%
Risk-free interest rate%	2.6%		2.6%
Expected dividend yield%		0.0%		0.0%

Summary of RSU Activity (Detail)

	RSUs
	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2018		1,736,234		$	9.65
RSUs granted		651,392			7.69
RSUs vested		(21,149	)		6.33
Unvested at March 31, 2019		2,366,477		$	9.14
Vested and unreleased		142,656
Outstanding at March 31, 2019		2,509,133

Summary of Stock-Based Compensation Expense

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

	Three Months Ended March 31, 2019
	2019		2018
Research and development	$	391	$	203
Selling and marketing		265		127
General and administrative		3,896		860
Total stock-based compensation expense	$	4,552	$	1,190