Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
	Jul. 31, 2020 USD ($)
Other Commitments [Line Items]
Contractual obligation remaining commitments including cancellation provisions	$ 3,400,000
Amounts associated with indemnifications	0
Maximum [Member]
Other Commitments [Line Items]
Royalty payable upon completion of first commercial sale of DME	$ 1,000,000
Royalty payment obligations expiration period	90 days
Indemnification Guarantee [Member]
Other Commitments [Line Items]
Contingent liabilities	$ 0