Equity Plans - Employee Stock Options Valuation Assumptions (Details) - Employee stock options	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity Plans
Expected volatility, Minimum	74.30%	62.00%	72.10%	62.00%
Expected volatility, Maximum	74.50%	62.70%	74.50%	62.70%
Risk-free interest rate, Minimum	0.39%	1.88%	0.39%	1.88%
Risk-free interest rate, Maximum	0.42%	2.20%	1.44%	2.58%
Minimum
Equity Plans
Expected term	5 years 6 months	5 years 6 months	5 years 3 months 7 days	5 years 6 months
Maximum
Equity Plans
Expected term	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days