Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 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		(2,624,505	)		2,624,505			8.19
Options exercised		—			(2,219,251	)		4.34
Options canceled		553,585			(553,585	)		6.73
Withheld shares to pay for taxes on RSU released shares		253,986
RSUs granted		(708,144	)
RSUs canceled		70,732
Balance at September 30, 2019		3,307,560			11,455,377		$	7.58		7.9	$	1,011
Vested and exercisable at September 30, 2019					4,575,393		$	6.25		6.2	$	1,010
Vested and expected to vest at September 30, 2019					10,793,250		$	7.38		7.7	$	1,010

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

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

	Nine Months Ended September 30,
	2019		2018
Expected term (in years)		6.0		6.0
Expected volatility%	60.7%		60.4%
Risk-free interest rate%	2.4%		2.8%
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		708,144			7.79
RSUs vested		(631,252	)		9.40
Unvested at September 30, 2019		1,813,126		$	9.13
Vested and unreleased		104,173
Outstanding at September 30, 2019		1,917,299

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 September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Research and development	$	377	$	511	$	1,221	$	1,061
Selling and marketing		368		234		980		555
General and administrative		4,165		6,434		12,168		8,436
Total stock-based compensation expense	$	4,910	$	7,179	$	14,369	$	10,052