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Schedule of Carrying Value of Trust Assets, Including Unrealized Gains or Losses (Detail) - USD ($) $ in Thousands | Sep. 30, 2017 | Mar. 31, 2017
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Investments held in Rabbi Trust | $ 8,846 |
Unrealized gain (losses) in fair value of trust assets | 82 |
Obligations under the supplemental plan | $ 30,631 |
Predecessor |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Investments held in Rabbi Trust |  | $ 8,759
Unrealized gain (losses) in fair value of trust assets |  | (95)
Unrealized losses in fair value of trust assets are net of income tax expense of |  | (223)
Obligations under the supplemental plan |  | $ 29,108

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