Income Taxes - Additional Information (Detail) - USD ($)	8 Months Ended	12 Months Ended			16 Months Ended
	Dec. 31, 2017	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2019
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		$ 124,000
Change in valuation allowance		1,600,000	$ 1,000,000	$ 3,000,000
NOL carryforwards		$ 5,000,000			$ 5,000,000
Federal income tax rate	35.00%	21.00%	30.40%	34.00%	21.00%
Reduction of deferred tax assets		$ 578,000
Unrecognized tax benefits		0	$ 0	$ 0	$ 0
Material changes in the next twelve months in unrecognized tax benefits		0			0
Interest and penalties related to uncertain tax positions		0	$ 0	$ 0
State Income Tax [Member]
Operating Loss Carryforwards [Line Items]
NOL carryforwards		$ 3,900,000			3,900,000
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		$ 33,300,000			$ 33,300,000