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Schedule of Unrealized (Loss) Gains in Carrying Value of Trust Assets (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Jul. 31, 2017 | Mar. 31, 2017
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Defined Benefit Plan Disclosure [Line Items] |  |  |
Unrealized gain (loss) in carrying value of trust assets | $ 256 |  |
Predecessor |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Unrealized gain (loss) in carrying value of trust assets |  | $ 82 | $ (95)
Unrealized loss in carrying value of trust assets are net of income tax expense of |  |  | $ (223)

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- Definition Trust assets carrying value income tax expense benefit. + References No definition available. + Details
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Namespace Prefix: | tdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Trust assets, carrying value, net + References No definition available. + Details
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Namespace Prefix: | tdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |