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, 2020
Jun. 30, 2019
Pension Plans, Defined Benefit [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service cost $ 116 $ 124
Interest cost 303 323
Expected return on assets (629) (664)
Amortization of actuarial loss 260 242
Net pension cost and postretirement benefit cost 50 25
Other Postretirement Benefit Plans [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Interest cost 5 5
Amortization of actuarial loss 6 7
Net pension cost and postretirement benefit cost $ 11 $ 12