13. Income Taxes (Details) - USD ($)		12 Months Ended
	Dec. 22, 2017	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
13. Income Taxes (Details) [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%			35.00%
Deferred Tax Assets, Operating Loss Carryforwards, Not Subject to Expiration		$ 23,000,000
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration		$ 4,000,000
Tax Credit Carryforward, Expiration Year		2023
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued		$ 64,000	$ 10,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense		54,000	3,000
Decrease in Unrecognized Tax Benefits is Reasonably Possible		$ 40,000
Minimum [Member]
13. Income Taxes (Details) [Line Items]
Tax Credit Carryforward, Expiration Year		2023
Maximum [Member]
13. Income Taxes (Details) [Line Items]
Tax Credit Carryforward, Expiration Year		2031
Domestic Tax Authority [Member]
13. Income Taxes (Details) [Line Items]
Operating Loss Carryforwards		$ 18,900,000
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] | Domestic Tax Authority [Member]
13. Income Taxes (Details) [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Period Increase (Decrease)		1,300,000
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] | Foreign Tax Authority [Member]
13. Income Taxes (Details) [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Period Increase (Decrease)			$ (9,400,000)
Investment Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
13. Income Taxes (Details) [Line Items]
Tax Credit Carryforward, Amount		$ 9,900,000