Balance Sheet Components - Intangible assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Intangible assets
Impairment	$ (4,000,000)	$ 0
Total intangible assets, net	26,023,889	31,710,556
Amortization expense	1,686,667	1,686,657
Developed technology
Intangible assets
Total intangible assets	25,000,000	25,000,000
Accumulated amortization	(4,027,778)	(2,361,111)
Finite-lived intangible assets, net	20,972,222	22,638,889
In process research and development
Intangible assets
Total intangible assets	8,800,000	8,800,000
Impairment	(4,000,000)
Finite-lived intangible assets, net	4,800,000	8,800,000
Trademarks
Intangible assets
Total intangible assets	300,000	300,000
Accumulated amortization	(48,333)	(28,333)
Total intangible assets, net	$ 251,667	$ 271,667