Commitments and Contingencies - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Apr. 30, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020 (remaining)	$ 347
2021	1,471
2022	1,445
2023	1,404
2024	1,419
Thereafter	4,400
Total	$ 10,486
Future Minimum Lease Payments [Abstract]
2020		$ 1,338
2021		1,471
2022		1,445
2023		1,404
2024		1,419
Thereafter		4,400
Total		$ 11,477