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 9 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Pension Plans, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 124 $ 142 $ 372 $ 428
Interest cost 322 335 968 1,005
Expected return on assets (663) (766) (1,992) (2,297)
Amortization of actuarial loss 242 212 726 635
Net pension cost and postretirement benefit cost 25 (77) 74 (229)
Other Postretirement Benefit Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 5 7 16 19
Amortization of actuarial loss 7 6 21 20
Net pension cost and postretirement benefit cost $ 12 $ 13 $ 37 $ 39