BENEFIT PLANS:- Additional information (Details)		1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares	Jan. 31, 2018 USD ($)	Apr. 30, 2021	Apr. 30, 2020 USD ($) employee shares	Apr. 30, 2019 USD ($)	Apr. 30, 2018 USD ($)	Dec. 29, 2017 $ / shares
Defined Benefit Plan Disclosure [Line Items]
Share-based Compensation, Total					$ 113,000	$ 231,000
Weighted-average remaining vesting period					1 year
Pension Benefit Plan Accelerated Funding					$ 11,688,000
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent					564,000	903,000
Expected lump sum payments from the pension funds					$ 2,929,000
Number of Former Employees | employee					309
Voluntary Contributions To The Pension Plan					$ 3,600,000
Estimated Pension Settlement Expenses Before Tax					$ 2,049,000	$ 903,000
Defined Benefit Plan Expected Future Benefit Payments For First Five Years Following Fiscal Year Description					The amount of future annual benefit payments to pension plan participants payable from plan assets is expected to be as follows: 2021 - $2,506,000, 2022 - $1,769,000, 2023 - $1,710,000, 2024 - $1,637,000 and 2025 - $1,576,000 and an aggregate of $7,003,000 is expected to be paid in the fiscal five-year period 2026 through 2030.
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets					7.75%	8.00%
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year					$ 529,000
Defined Benefit Plan, Expected Amortization of Transition Asset (Obligation), Next Fiscal Year					0
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year					0
Defined Benefit Plan, Benefit Obligation					23,274,000	$ 30,304,000	$ 32,423,000
Defined Benefit Plan, Plan Assets, Amount					18,260,000	23,903,000	$ 23,372,000
Defined Benefit Pension Plan, Liabilities					5,014,000	6,401,000
Accrued Pension Related Obligation					5,194,000
Deferred Compensation Arrangement with Individual, Allocated Share-based Compensation Expense					33,000	27,000
Defined Benefit Plan, Plan Assets, Contributions by Employer					3,600,000	2,000,000
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation					5,014,000	6,401,000
Defined Benefit Plan, Plan Assets, Amount					18,260,000	23,903,000
Simple Internal Revenue Code, Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer					14,000
Defined Contribution Plan, Employer Discretionary Contribution Amount					$ 5,000
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent					3.00%
Board of Directors Chairman [Member]
Defined Benefit Plan Disclosure [Line Items]
Non Cash Director Fee Compensation					$ 100,000	80,000
Scenario, Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets				7.75%
Equity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Share-based Compensation, Total					113,000	$ 151,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total					$ 49,000
Two Thousand Six 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 | shares					500,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | shares					391,619
2016 Equity Plan [Member] | Board of Directors Chairman [Member]
Defined Benefit Plan Disclosure [Line Items]
Shares Issued, Price Per Share | $ / shares	$ 5.98	$ 5.95						$ 25,000.00
Non Cash Director Compensation			$ 20,000
Stock Issued During Period, Shares, Restricted Stock Award, Gross | shares	16,720	13,444
Weighted Average [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate					2.29%	3.54%
PBGC [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits					$ 3,600,000
PBGC [Member] | Equity Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Payment for Pension Benefits						$ 2,000,000