Convertible Senior Notes - Interest Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2021	Oct. 31, 2020
Debt Instrument [Line Items]
Non-cash interest expense	$ 4,773	$ 1,952
Convertible Debt | 2023 Convertible Senior Notes
Debt Instrument [Line Items]
Interest expense related to amortization of debt discount	0	7,725
Interest expense related to amortization of debt issuance costs	400	431
Total interest expense	400	8,156
Convertible Debt | 2026 Convertible Senior Notes
Debt Instrument [Line Items]
Interest expense related to amortization of debt discount	8,320	3,187
Interest expense related to amortization of debt issuance costs	951	365
Non-cash interest expense	4,773	1,952
Total interest expense	14,044	$ 5,504
Convertible Debt | 2027 Convertible Senior Notes
Debt Instrument [Line Items]
Contractual interest expense	152
Interest expense related to amortization of debt issuance costs	160
Total interest expense	$ 312