BENEFIT PLANS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Decrease in pension liability, net of tax ($42 in 2020 and $43 in 2019)	$ 90,000	$ 98,000	$ 180,000	$ 252,000
Voluntary Contributions To The Pension Plan	1,847,000	3,600,000	1,847,000	3,600,000
Payment for Pension Benefits				7,280,000
Expected lump sum payments from the pension funds	$ 0	2,929,000	0	2,929,000
Share-based Compensation, Total			42,000	107,000
Number of common stock issued to directors for settlement of deferred stock units	12,411
Cash paid to directors in lieu of issuance of deferred common share units			20,000
Non employee Individual of Board of Directors [Member]
Defined Benefit Plan Disclosure [Line Items]
Non-cash expense related to deferred common share units	$ 21,000	$ 23,000	$ 35,000	$ 53,000
Equity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period			12,834	14,833
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	29,000	36,834	29,000	36,834
Two Thousand Six Equity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Stock Issued During Period, Shares, Restricted Stock Award, Gross			9,000	9,000
Restricted Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Share-based Compensation, Total	$ 25,000	$ 30,000	$ 7,000	$ 54,000
Restricted Stock [Member] | Equity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 73,000	$ 135,000	$ 73,000	$ 135,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years