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Schedule of Unrecognized Tax Benefits Which Would Lower Effective Tax Rate if Realized (Detail) - State and Local Jurisdiction $ in Thousands	6 Months Ended
	Sep. 30, 2017 USD ($)
Income Tax Contingency [Line Items]
Unrecognized tax benefit related to state tax issues	$ 12,367
Interest receivable on unrecognized tax benefit related to state tax issues	$ 52

X

- Definition

This element represents an interest income receivable on an uncertain tax position.

+ References

No definition available.

+ Details

Name:	tdw_UnrecognizedTaxBenefitInterestIncomeReceivable
Namespace Prefix:	tdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The gross amount of unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return.

+ References

No definition available.

+ Details

Name:	tdw_UnrecognizedTaxBenefitsCurrentAndPriorPeriodTaxPositions
Namespace Prefix:	tdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- 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

Name:	us-gaap_IncomeTaxContingencyLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_StateAndLocalJurisdictionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: