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Amounts Charged to Expense Related to Defined Contribution Plans (Detail) - Defined Contribution Savings Plan 401k - USD ($) $ in Thousands | 4 Months Ended | 5 Months Ended | 12 Months Ended
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Jul. 31, 2017 | Dec. 31, 2017 | Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined contribution plans expense, net of forfeitures |  | $ 854 |
Defined contribution plans forfeitures |  | $ 83 |
Predecessor |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined contribution plans expense, net of forfeitures | $ 871 |  | $ 2,660
Defined contribution plans forfeitures | $ 79 |  | $ 149

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- Definition Defined Benefit Plan Forfeited Amounts + References No definition available. + Details
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Namespace Prefix: | tdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Defined Contribution Plan Expense + References No definition available. + Details
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Namespace Prefix: | tdw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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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_
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Period Type: | duration

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

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