Common Stock and Preferred Stock - Shares Reserved for Future Issuance (Details) - shares	Mar. 31, 2020	Dec. 31, 2019	Jan. 31, 2017
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	8,723,000	7,483,000	1,753,758
Restricted Stock Units (RSUs)
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	760,000	460,000
Outstanding Employee Stock Options
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	6,643,000	5,735,000
Future Issuances from Employee Stock Options
Conversion of Stock [Line Items]
Common stock reserved for potential conversion (in shares)	1,320,000	1,288,000