BENEFIT PLANS - Fair value hierarchy of pension plan's assets at fair value (Details) - USD ($)	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Defined Benefit Plan, Fair Value of Plan Assets	$ 18,054,000	$ 21,102,000	$ 18,260,000
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	18,054,000	21,102,000
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Cash Equivalents [Member]
Defined Benefit Plan, Fair Value of Plan Assets	791,000	2,215,000
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	791,000	2,215,000
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Equity Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	10,348,000	10,707,000
Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	10,348,000	10,707,000
Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fixed Income Securities [Member]
Defined Benefit Plan, Fair Value of Plan Assets	6,915,000	8,180,000
Fixed Income Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	6,915,000	8,180,000
Fixed Income Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Fixed Income Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0	$ 0