Balance Sheet Components - Intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible assets
Impairment	$ 0	$ (4,000)
Total intangible assets, net	24,337	26,024
Amortization expense	1,700	1,700
Developed technology
Intangible assets
Total intangible assets	25,000	25,000
Accumulated amortization	(5,694)	(4,028)
Finite-lived intangible assets, net	19,306	20,972
In process research and development
Intangible assets
Total intangible assets	4,800	8,800
Impairment		(4,000)
Finite-lived intangible assets, net	4,800	4,800
Trademarks
Intangible assets
Total intangible assets	300	300
Accumulated amortization	(69)	(48)
Total intangible assets, net	$ 231	$ 252