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
Jun. 30, 2021
Jun. 30, 2020
Pension Plans, Defined Benefit [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service cost $ 93 $ 116
Interest cost 300 303
Expected return on assets (682) (629)
Amortization of actuarial loss 213 260
Net pension cost and postretirement benefit cost (76) 50
Other Postretirement Benefit Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Interest cost 3 5
Amortization of actuarial loss 6 6
Net pension cost and postretirement benefit cost $ 9 $ 11