Quarterly report pursuant to Section 13 or 15(d)

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

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Employee Benefit Plans - Components of Postretirement Benefit Cost and Pension Cost (Detail) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Pension Plans, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 94 $ 115 $ 187 $ 231
Interest cost 298 303 598 606
Expected return on assets (682) (628) (1,364) (1,257)
Amortization of actuarial loss 229 260 442 520
Net pension cost and postretirement benefit cost (61) 50 (137) 100
Other Postretirement Benefit Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 4 4 7 9
Amortization of actuarial loss 6 7 12 13
Net pension cost and postretirement benefit cost $ 10 $ 11 $ 19 $ 22