Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Stock Option Activity

		Options Outstanding
			Weighted-		Weighted-
			Average		Average
	Options		Exercise		Remaining	Aggregate
	Available for	Number of	Price Per		Contractual	Intrinsic
	Grant	Options	Share		Life (years)	Value
						(In thousands)
Balance—December 31, 2015	55,330	927,175	$	4.43	7.3	$	6,500
Options authorized	785,364	—
Options granted	(563,523)	563,523		13.20
Options exercised	—	(10,639)		4.43		$	114
Options cancelled/forfeited	65,329	(65,329)		4.71
Balance—December 31, 2016	342,500	1,414,730	$	5.28	7.6	$	4,267
Options authorized	374,944	—
RSUs granted	(30,680)	—
Options granted	(757,900)	757,900		13.02
Options exercised	—	(281,483)		4.75		$	2,101
Options cancelled/forfeited	155,065	(297,952)		6.13
Balance—December 31, 2017	83,929	1,593,195		8.88	6.6	$	1,997
Options exercisable—December 31, 2017		766,233		5.43	3.7	$	1,825
Options vested and expected to vest—December 31, 2017		1,593,195		8.88	6.6	$	1,997

Schedule of Restricted Stock Unit Activity

	RSUs Outstanding
		Weighted-
		Average
	Number of	Exercise
	Restricted Stock	Price Per
	Units	Share
Balance—December 31, 2016	—	$	—
Granted	30,680		10.55
Balance—December 31, 2017	30,680	$	10.55

Summary of Stock-Based Compensation Expense

The Company recognized stock-based compensation expense as follows (in thousands):

	Year Ended December 31,
	2017		2016		2015
Research and development	$	488	$	403	$	169
General and administrative		1,297		637		190
Sales and marketing		263		101		57
Total	$	2,048	$	1,141	$	416

2016 Employee Stock Purchase Plan

Schedule of Fair Value Assumptions

	Year Ended December 31,
	2017		2016		2015
Expected volatility	49.3 – 72.7	%	—	%	—	%
Risk-free interest rate	0.49 – 1.02	%	—	%	—	%
Expected term (in years)	0.5 – 1.0		—		—
Dividend yield	—	%	—	%	—	%

Employees

Schedule of Fair Value Assumptions

	Year Ended December 31,
	2017		2016		2015
Expected volatility	46.7 – 52.0	%	42.6 – 45.3	%	44.1 – 48.9	%
Risk-free interest rate	1.85 - 2.14	%	1.12 – 2.26	%	1.51 – 1.79	%
Expected term (in years)	5.3 – 6.1		4.8 – 6.1		5.6 – 6.1
Dividend yield	—	%	—	%	—	%

Non-Employee

Schedule of Fair Value Assumptions

	Year Ended December 31,
	2017		2016	2015
Expected volatility	46.7 – 60.5		52.3 – 52.7	51.6 – 52.9	%
Risk-free interest rate	2.09 – 2.44		1.94 – 2.41	1.72 – 2.02	%
Expected term (in years)	7.2 – 9.6		9.5 – 9.8	6.6 – 9.1
Dividend yield	—	%	—	—	%