BENEFIT PLANS: (Details 5)	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Schedule Of Allocation Of Plan Assets [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	100.00%	100.00%
Equity Securities [Member]
Schedule Of Allocation Of Plan Assets [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	69.00%	67.00%
Cash Equivalents [Member]
Schedule Of Allocation Of Plan Assets [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	2.00%	5.00%
Fixed Income Securities [Member]
Schedule Of Allocation Of Plan Assets [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations	29.00%	28.00%