Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ (124,000)	$ 124,000
Change in valuation allowance	1,100,000	1,600,000	$ 1,000,000
NOL carryforwards	5,000,000
Provision for unrecognized tax benefits	0	$ 0	$ 0
Federal Income Tax [Member]
Operating Loss Carryforwards [Line Items]
NOL carryforwards	312,000
Federal Income Tax [Member] | Carried Forward Indefinitely [Member]
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 1,700,000
Federal Income Tax [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards expiration period	2024
State Income Tax [Member]
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 5,900,000
State Income Tax [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carry forwards expiration period	2036
U.K. Income Tax [Member]
Operating Loss Carryforwards [Line Items]
NOL carryforwards	$ 37,100,000