Quarterly report pursuant to Section 13 or 15(d)

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

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Employee Benefit Plans - Components of Postretirement Benefit Cost and Pension (Income) Cost (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Pension Plans, Defined Benefit [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 142 $ 149 $ 428 $ 448
Interest cost 335 356 1,005 1,067
Expected return on assets (766) (743) (2,297) (2,232)
Amortization of actuarial loss 212 253 635 760
Net pension (income) cost and postretirement benefit cost (77) 15 (229) 43
Other Postretirement Benefit Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 7 6 19 19
Amortization of actuarial loss 6 9 20 28
Net pension (income) cost and postretirement benefit cost $ 13 $ 15 $ 39 $ 47