Common Stock, Common Stock Warrants and Stock Option Plan (Tables)

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

Schedule of Stock Reserved for Future Issuance

	March 31,	December 31,
	2020	2019
Warrants to purchase common stock	1,165,282	1,165,282
Options outstanding	1,626,244	1,929,391
Restricted stock units outstanding	2,253,181	1,451,507
Shares available for future grants	557,671	288,813
Shares available for ESPP	547,513	373,428
Shares reserved for issuance upon conversion of the Notes	8,885,204	8,885,204
Total	15,035,095	14,093,625

Summary of Outstanding Common Stock Warrants

As of March 31, 2020
Total amount of securities issuable
under the outstanding warrants	Exercise Price		Issuance Date	Expiration Date
315,282	$	2.38	2014-2015	2022-2024
850,000	$	8.62	2018	2024
1,165,282	$	6.93

Summary of Stock Option Activity

	Stock Options
				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
	Shares	Price		Term (Years)	Value
	(aggregate intrinsic value in thousands)
Outstanding as of December 31, 2017	1,560,453	$	3.63	7.6	$	4,632
Granted	479,375		7.25
Exercised	(112,965)		2.48
Canceled	(61,448)		3.65
Outstanding as of December 31, 2018	1,865,415		4.63	7.6	$	1,540
Granted	189,856		6.16
Exercised	(112,647)		3.36
Canceled	(13,233)		6.53
Outstanding as of December 31, 2019	1,929,391		4.84	6.9	$	7,146
Granted	—		—
Exercised	(299,737)		3.91
Canceled	(3,410)		6.94
Outstanding as of  March 31, 2020	1,626,244	$	5.01	6.9	$	10,057
Options vested and expected to vest as of March 31, 2020	1,582,822	$	4.97	6.9	$	9,849
Options vested and exercisable as of March 31, 2020	1,034,771	$	4.42	6.3	$	7,002

Summary of Restricted Stock Units Activity

	Restricted Stock Units
				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
		Grant Date		Contractual	Intrinsic
	Shares	Fair Value		Term (Years)	Value
	(aggregate intrinsic value in thousands)
Outstanding as of December 31, 2017	509,894	$	2.84	1.4	$	3,288
Granted	925,578		6.55
Released	(264,568)		4.02
Forfeited/expired	(15,924)		8.34
Outstanding as of December 31, 2018	1,154,980		5.50	1.4	$	5,082
Granted	978,851		6.35
Released	(512,703)		5.31
Forfeited/expired	(169,621)		5.15
Outstanding as of December 31, 2019	1,451,507		6.18	1.3	$	12,314
Granted	958,825		7.88
Released	(143,625)		5.40
Forfeited/expired	(13,526)		7.67
Outstanding as of March 31, 2020	2,253,181	$	6.94	1.5	$	25,182