Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 25
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=109244457&loc=d3e16701-113920

+ Details

Name:	us-gaap_CommonStockSharesHeldInEmployeeTrustShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

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

- Details

Name:	us-gaap_RetirementPlanNameAxis=tdw_DefinedContributionSavingPlanFourZeroOneKMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_PredecessorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=us-gaap_SeriesAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=us-gaap_SeriesBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Number of Tidewater Common Stock Shares, Series A Warrants and Series B Warrants Held by Plan (Detail) - shares	Dec. 31, 2018	Dec. 31, 2017	Jul. 31, 2017	Mar. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Number of shares of Tidewater common stock held by 401(k) plan	7,075
Warrants issued	2,547	924,125
Defined Contribution Savings Plan 401k
Defined Contribution Plan Disclosure [Line Items]
Number of shares of Tidewater common stock held by 401(k) plan		8,074
Defined Contribution Savings Plan 401k \| Predecessor
Defined Contribution Plan Disclosure [Line Items]
Number of shares of Tidewater common stock held by 401(k) plan			264,504	291,957
Defined Contribution Savings Plan 401k \| Series A Warrants
Defined Contribution Plan Disclosure [Line Items]
Warrants issued		9,030
Defined Contribution Savings Plan 401k \| Series B
Defined Contribution Plan Disclosure [Line Items]
Warrants issued		9,762