Stockholders' Equity - Common Stock Reserved For Future Issuance (Details) - shares shares in Thousands	Jan. 31, 2020	Jan. 31, 2019
Class of Stock [Line Items]
Reserved for future issuance (in shares)	50,839	52,525
RSUs
Class of Stock [Line Items]
Reserved for future issuance (in shares)	14,246	17,558
Stock options
Class of Stock [Line Items]
Reserved for future issuance (in shares)	6,882	13,648
ESPP
Class of Stock [Line Items]
Reserved for future issuance (in shares)	4,985	3,800
Remaining shares available for future issuance under the Equity Incentive Plans
Class of Stock [Line Items]
Reserved for future issuance (in shares)	24,726	17,519