Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Oct. 31, 2020	Jul. 31, 2020	May 01, 2020	Apr. 30, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
Decrease in accumulated deficit, from ASU 2016-13 adoption	$ 442,657	$ 432,379		$ 413,647	$ 433,156	$ 255,050	$ 263,012
Accumulated Deficit
Summary Of Significant Accounting Policies [Line Items]
Decrease in accumulated deficit, from ASU 2016-13 adoption	$ (532,043)	$ (502,885)		(484,251)	$ (408,819)	$ (358,846)	$ (317,077)
Cumulative Effect, Period of Adoption, Adjustment
Summary Of Significant Accounting Policies [Line Items]
Decrease in accumulated deficit, from ASU 2016-13 adoption				367
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
Summary Of Significant Accounting Policies [Line Items]
Decrease in accumulated deficit, from ASU 2016-13 adoption			$ 400	$ 367