Stockholders' Equity - Schedule of Reserved Shares of Common Stock for Future Issuances (Details) shares in Thousands	Sep. 30, 2019 shares
Class Of Stock [Line Items]
Total reserved shares of common stock	35,595
Equity Incentive Plan
Class Of Stock [Line Items]
Common stock awards granted under equity incentive plans	16,189
Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common stock awards available for issuance	2,089
2017 Plan
Class Of Stock [Line Items]
Common stock awards available for issuance	17,317