Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Components of Postretirement Benefit Expense (Income) and Pension Cost (Benefit) (Detail)

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Employee Benefit Plans - Components of Postretirement Benefit Expense (Income) and Pension Cost (Benefit) (Detail) - Other Postretirement Benefit Plans [Member] - USD ($)
$ in Thousands
 12 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]      
Interest cost on accumulated benefit obligation $ 18 $ 22 $ 25
Amortization of actuarial loss 27 28 28
Net pension (benefit) cost and postretirement benefit expense $ 45 $ 50 $ 53