Balance Sheet Components - Intangible assets (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Intangible assets
Impairment	$ 0	$ (4,000,000)	$ 0	$ (4,000,000)
Finite-lived intangible assets, net	25,181,000		25,181,000		$ 26,024,000
Total intangible assets, net	25,181,000		25,181,000		26,024,000
Amortization expense	422,000	843,000	422,000	843,000
Developed technology
Intangible assets
Total intangible assets	25,000,000		25,000,000		25,000,000
Accumulated amortization	(4,861,000)		(4,861,000)		(4,028,000)
Finite-lived intangible assets, net	20,139,000		20,139,000		20,972,000
In process research and development
Intangible assets
Total intangible assets	4,800,000		4,800,000		8,800,000
Impairment		$ 4,000,000		$ 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	(58,000)		(58,000)		(48,000)
Finite-lived intangible assets, net	$ 242,000		$ 242,000		$ 252,000