INCOME TAXES: - Additional information (Details) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2018	Apr. 30, 2038	Apr. 30, 2019
Operating Loss Carryforwards State Subject To Expiration Current	$ 118,209,000
Unrecognized Tax Benefits, Period Increase (Decrease)		$ 58,000
Income Tax Examination, Penalties and Interest Accrued	0			$ 0
Operating Loss Carryforwards	17,838,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 262,000
Scenario, Forecast [Member]
Operating Loss Carryforwards			$ 147,000