Balance Sheet Components - Intangible assets (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Intangible assets
Impairment	$ 0	$ 0	$ 0	$ (4,000,000)
Total intangible assets, net	24,759,000		24,759,000		$ 26,024,000
Amortization expense	422,000	1,265,000	422,000	1,265,000
Developed technology
Intangible assets
Total intangible assets	25,000,000		25,000,000		25,000,000
Accumulated amortization	(5,278,000)		(5,278,000)		(4,028,000)
Finite-lived intangible assets, net	19,722,000		19,722,000		20,972,000
In process research and development
Intangible assets
Total intangible assets	4,800,000		4,800,000		8,800,000
Impairment		$ 0		$ 4,000,000	(4,000,000)
Finite-lived intangible assets, net	4,800,000		4,800,000		4,800,000
Trademarks
Intangible assets
Total intangible assets	300,000		300,000		300,000
Accumulated amortization	(63,000)		(63,000)		(48,000)
Finite-lived intangible assets, net	$ 237,000		$ 237,000		$ 252,000