Employee Benefit Plans - Components of Postretirement Benefit Expense (Income) and Pension (Benefit) Cost (Detail) - Other Postretirement Benefit Plans [Member] - USD ($) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
Mar. 31, 2016 |
|
Defined Benefit Plan Disclosure [Line Items] | |||
Interest cost on accumulated benefit obligation | $ 26 | $ 26 | $ 29 |
Amortization of actuarial loss | 37 | 36 | 40 |
Net pension cost (benefit) | $ 63 | $ 62 | $ 69 |