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Employee Benefit Plans - Additional Information (Detail) | 12 Months Ended
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Mar. 31, 2019 USD ($) $ / Employee | Mar. 31, 2018 USD ($) | Mar. 31, 2017 USD ($)
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 | $ 30,380,000 | $ 30,385,000 |
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 | 2024 |  |
Medical care cost trend rate decrements | 0.50% |  |
Current portion of accrued postretirement benefit obligation | $ 78,000 | 81,000 |
Company contributions to the ESOP |  |  | $ 0
Stop loss coverage per employee for claims | $ / Employee | 100 |  |
Maximum aggregate stop loss coverage | $ / Employee | 1,000 |  |
Total plan amount | $ 2,399,000 |  |
Self-Insured medical plan liability | 150,000 | 122,000 |
Defined Contribution Plan 401K [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions to defined contribution plan | $ 1,135,000 | $ 805,000 | 873,000
Equity Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target Plan Asset Allocations | 50.00% | 65.00% |
Debt Securities [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Target Plan Asset Allocations | 50.00% | 35.00% |
Pension Plans, Defined Benefit [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions expected during fiscal 2020 | $ 0 |  |
Liability released through annuity purchase | 1,589,000 | $ 890,000 |
Annuities purchased | 1,718,000 | 998,000 |
Estimated net actuarial loss for pension plan | 969,000 |  |
Pension expense | $ (305,000) | $ 57,000 | $ 528,000
Weighted average discount rates used to develop net postretirement benefit cost | 3.95% | 4.08% | 3.93%
Defined Contribution Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Contributions to defined contribution plan | $ 325,000 | $ 284,000 | $ 286,000
Supplemental Executive Retirement Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension expense | 97,000 | 115,000 | 128,000
Pension expense related liability | 662,000 | 582,000 |
Current portion of the related liability included in accrued compensation | 0 | 17,000 |
Other Postretirement Benefit Plans [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Estimated net actuarial loss for pension plan | 28,000 |  |
Pension expense | $ 53,000 | $ 63,000 | $ 62,000
Weighted average discount rates used to develop net postretirement benefit cost | 3.63% | 3.23% | 3.16%

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- Definition Aggregate annual stop loss coverage for the entire medical plan. + References No definition available. + Details
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- Definition Company's share of the medical premium cost for early retirees for family coverage under the other postretirement plan. + References No definition available. + Details
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- Definition Company's share of the medical premium cost for early retirees for single coverage under the other postretirement plan. + References No definition available. + Details
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