Stockholders' Equity - Common Stock Reserved for Future Issuance (Details) shares in Thousands	Dec. 31, 2019 shares
Class of Stock [Line Items]
Shares of common stock reserved for future issuance (in shares)	16,801
Shares available for future grant under 2014 Plan
Class of Stock [Line Items]
Shares of common stock reserved for future issuance (in shares)	9,814
Stock options outstanding
Class of Stock [Line Items]
Shares of common stock reserved for future issuance (in shares)	2,530
Restricted stock units outstanding
Class of Stock [Line Items]
Shares of common stock reserved for future issuance (in shares)	2,372
Shares available for future issuance under ESPP
Class of Stock [Line Items]
Shares of common stock reserved for future issuance (in shares)	2,085