Represents amount of consent solicitation and concurrent tender offer under debt instrument agreement.

No definition available.

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

- Definition

Represents maximum cumulative prepayment of debt under debt instrument agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	tdw_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of mandatory tender offer.

+ References

No definition available.

+ Details

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

- Definition

The amount of premium (discount) on repurchased debt instrument.

+ References

No definition available.

+ Details

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

- Definition

The percent of net proceeds from asset dispositions that are held as restricted cash.

+ References

No definition available.

+ Details

Name:	tdw_PercentOfNetProceedsFromAssetDispositionsRestrictedCash
Namespace Prefix:	tdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

+ Details

Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchasedFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=121583591&loc=SL98516268-108586

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

+ Details

Name:	us-gaap_RestrictedCashCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=tdw_The800SeniorSecuredNotesDueAugust2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tdw_TromsOffshoreBorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=tdw_TromsOffshoreMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
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Period Type:

Note 9 - Debt (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
Note 9 - Debt (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2021	Nov. 03, 2020	Sep. 30, 2020	Dec. 31, 2019
Restricted Cash, Current					$ 26,401	$ 5,755
Percent of Net Proceeds From Asset Dispositions, Restricted Cash					65.00%
The 8.00% Senior Secured Notes due August 2022 [Member]
Debt Instrument, Mandatory Tender Offer					$ 28,700
Debt Instrument, Repurchased Face Amount					27,700
Debt Instrument, Repurchase Premium (Discount) Amount					$ (1,500)
The 8.00% Senior Secured Notes due August 2022 [Member] \| Subsequent Event [Member]
Debt Instrument, Consent Solicitation and Concurrent Tender Offer				$ 50,000
Troms Offshore Borrowings [Member] \| Forecast [Member]
Repayments of Long-term Debt, Total	$ 12,400	$ 8,000
Debt Instrument, Covenant, Cumulative Prepayment of Debt, Maximum			$ 35,000
Troms Offshore Borrowings [Member] \| Troms Offshore [Member]
Debt, Weighted Average Interest Rate					5.00%
Fair Value, Inputs, Level 2 [Member] \| The 8.00% Senior Secured Notes due August 2022 [Member]
Debt Instrument, Fair Value Disclosure, Total					$ 193,900	237,600
Fair Value, Inputs, Level 2 [Member] \| Troms Offshore Borrowings [Member] \| Troms Offshore [Member]
Debt Instrument, Fair Value Disclosure, Total					$ 62,600	$ 72,900