Equity Plans - Employee Stock Options Valuation Assumptions (Details) - Employee stock options	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity Plans
Expected volatility, Minimum	72.10%	62.20%
Expected volatility, Maximum	73.80%	62.60%
Risk-free interest rate, Minimum	0.59%	2.45%
Risk-free interest rate, Maximum	1.44%	2.58%
Minimum
Equity Plans
Expected term	5 years 3 months 7 days	6 years 7 days
Maximum
Equity Plans
Expected term	6 years 29 days	6 years 29 days