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Summary of Debt Outstanding (Parenthetical) (Detail) - Level 2 - USD ($) $ in Millions | Sep. 30, 2017 | Mar. 31, 2017
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Term loan, revolving line of credit and senior notes |  |
Debt [Line Items] |  |
Fair value of debt |  | $ 1,100.0
New Secured Notes |  |
Debt [Line Items] |  |
Fair value of debt | $ 357.7 |
Troms Offshore borrowings |  |
Debt [Line Items] |  |
Fair value of debt | $ 90.9 | $ 92.9

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