Stockholders' Equity (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Common Stock
Options issued and outstanding (in shares)	5,988,461	5,562,484
Total number of shares reserved for issuance (in shares)	9,300,887	7,690,456
Shares of common stock subject to outstanding options
Common Stock
Shares available for issuance (in shares)	3,200,200	1,954,804
ESPP (in shares)
Common Stock
Shares available for issuance (in shares)	112,226	173,168