Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Additional Information (Detail)

v3.20.1
Employee Benefit Plans - Additional Information (Detail)
 12 Months Ended
Mar. 31, 2020
USD ($)
$ / Employee
Mar. 31, 2019
USD ($)
Mar. 31, 2018
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Employee's years of service and average earnings Five highest consecutive calendar years of compensation in the ten-year period preceding retirement    
Accumulated benefit obligation $ 31,715,000 $ 30,380,000  
Contribution equal to employee salary deferral 100.00%    
Employer contribution description Matching contributions equal to 100% of the first 3% of an employee's salary deferral and 50% of the next 2% percent of an employee's salary deferral    
Contribution next to employee salary deferral 3.00%    
Contribution for additional employee salary deferral 50.00%    
Contribution additional next to employee salary deferral 2.00%    
Share of the medical premium cost for family coverage $ 4,000    
Share of the medical premium cost for single coverage 2,000    
Share of the medical premium both family and single coverage for regular retirees $ 1,000    
Medical care cost trend rate 4.50%    
Medical care trend year 2025    
Medical care cost trend rate decrements 0.50%    
Current portion of accrued postretirement benefit obligation $ 77,000 78,000  
Stop loss coverage per employee for claims | $ / Employee 100,000    
Maximum aggregate stop loss coverage | $ / Employee 1,000    
Total plan amount $ 2,592,000    
Self-Insured medical plan liability 124,000 150,000  
Defined Contribution Plan 401K [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Contributions to defined contribution plan $ 1,000,000 $ 1,135,000 $ 805,000
Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target Plan Asset Allocations 30.00% 50.00%  
Debt Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Target Plan Asset Allocations 70.00% 50.00%  
Pension Plans, Defined Benefit [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Contributions expected during fiscal 2020 $ 0    
Liability released through annuity purchase 1,420,000 $ 1,589,000  
Annuities purchased 1,420,000 1,718,000  
Estimated net actuarial loss for pension plan 1,039,000    
Pension expense $ 98,000 $ (305,000) $ 57,000
Weighted average discount rates used to develop net postretirement benefit cost 3.83% 3.95% 4.08%
Defined Contribution Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Contributions to defined contribution plan $ 406,000 $ 325,000 $ 284,000
Supplemental Executive Retirement Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Pension expense 85,000 97,000 115,000
Pension expense related liability 747,000 662,000  
Other Postretirement Benefit Plans [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Estimated net actuarial loss for pension plan 27,000    
Pension expense $ 50,000 $ 53,000 $ 63,000
Weighted average discount rates used to develop net postretirement benefit cost 3.37% 3.63% 3.23%