Annual report pursuant to Section 13 and 15(d)

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

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Employee Benefit Plans - Components of Postretirement Benefit Cost (Income) and Pension Cost (Benefit) (Detail) - Pension Plans, Defined Benefit [Member] - USD ($)
$ in Thousands
12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]      
Service cost during the period $ 598 $ 600 $ 521
Interest cost on projected benefit obligation 1,423 1,450 1,437
Expected return on assets (2,977) (2,873) (3,181)
Actuarial loss 1,013 1,351 1,174
Net pension cost (benefit) $ 57 $ 528 $ (49)