Fair Value Measurements - Schedule of Carrying Amounts and Estimated Fair Values of Convertible Note (Details) - Senior Notes $ in Thousands	Apr. 30, 2020 USD ($)
Net Carrying Amount | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Convertible senior notes	$ 103,911
Net Carrying Amount | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Convertible senior notes	859,889
Estimated Fair Value | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Convertible senior notes	375,264
Estimated Fair Value | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Convertible senior notes	$ 1,126,769