Common Stock Warrants (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Schedule of Warrants Outstanding

Common stock warrants outstanding as of December 31, 2019 are as follows:

Holder	Issue Date	Outstanding Shares	Exercise Price		Exercisable Shares	Expiration Date
	(in thousands, except per share data)
Partner	3/1/2015	695	$	2.28	695	2/28/2025
		695			695

Common stock warrants outstanding as of December 31, 2018 are as follows:

Holder	Issue Date	Outstanding Shares	Exercise Price		Exercisable Shares	Expiration Date
	(in thousands, except per share data)
Bank	4/16/2015	28	$	0.36	28	9/5/2024
Bank	4/16/2015	63	$	0.80	63	4/16/2025
Partner	3/1/2015	694	$	2.28	694	2/28/2025
		785			785

Warrant activities during the years ended December 31, 2019, 2018 and 2017 were:

	Shares
	(in thousands)
Balance as of January 1, 2017	2,188
Exercised	(361	)
Forfeited or expired	(1,042	)
Balance as of December 31, 2017	785
Exercised, forfeited or expired	—
December 31, 2018	785
Exercised	(90	)
December 31, 2019	695