Debt instrument maturity year.

No definition available.

Name:	tdw_DebtInstrumentMaturityYear
Namespace Prefix:	tdw_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Modification description of debt instrument.

+ References

No definition available.

+ Details

Name:	tdw_ModificationDescriptionOfDebtInstrument
Namespace Prefix:	tdw_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of vessels mortgaged.

+ References

No definition available.

+ Details

Name:	tdw_NumberOfVesselsMortgaged
Namespace Prefix:	tdw_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of asset sale proceeds used to repurchase notes at par amount.

+ References

No definition available.

+ Details

Name:	tdw_PercentageOfAssetSaleProceedsUsedToRepurchaseNotesAtParAmount
Namespace Prefix:	tdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of required principal payments due from effective date.

+ References

No definition available.

+ Details

Name:	tdw_PercentageOfRequiredPrincipalPaymentsDueFromEffectiveDate
Namespace Prefix:	tdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Prepackaged plan effective date.

+ References

No definition available.

+ Details

Name:	tdw_PrepackagedPlanEffectiveDate
Namespace Prefix:	tdw_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Discussion of whether the debt instrument is secured or unsecured, and, if secured, a description of the collateral and guarantees required or provided.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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

- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

+ Details

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

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- 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

Discussion of the facts and amounts pertaining to each failure to comply with an affirmative or negative covenant of a long-term debt instrument, including violating payment terms or an inability to meet certain minimum financial requirements or achieve or maintain certain financial ratios. The discussion would generally be expected to also include whether or not the failure can and will be overcome and a description of the terms of any waivers, including the amount of the waiver and the period of time covered by the waiver, and if reclassification of long-term debt to current has been made in the current balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6802200&loc=SL6230698-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(c))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=tdw_TermLoanRevolvingLineOfCreditAndSeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=tdw_PlanOfReorganizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=tdw_TromsOffshoreSupplyAsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness - Additional Information (Detail) $ in Millions		1 Months Ended	4 Months Ended
	Jul. 31, 2017 USD ($) Vessel	Jul. 31, 2017 USD ($) Vessel	Jul. 31, 2017 USD ($) Vessel	Sep. 30, 2017
Debt [Line Items]
Debt instrument fixed interest rate	8.00%	8.00%	8.00%
Aggregate principal amount	$ 350	$ 350	$ 350
Debt instrument maturity year	2022
Term loan, revolving line of credit and senior notes
Debt [Line Items]
Interest expense that would have been resulted if debt was not compromised			$ 27
Plan of Reorganization \| Troms Offshore borrowings \| Senior Notes
Debt [Line Items]
Plan effective date	Jul. 31, 2017
Modification description of debt instrument	(i) reduce by 50% the required principal payments due from the Effective Date through March 31, 2019, (ii) modestly increase the interest rates on amounts outstanding through April 2023, and (iii) provide for security and additional guarantees, including (a) mortgages on six vessels and related assignments of earnings and insurances, (b) share pledges by Troms Offshore and certain subsidiaries of Troms Offshore, and (c) guarantees by certain subsidiaries of Troms Offshore.
Percentage of required principal payments due from effective date	50.00%
Number of vessels mortgaged \| Vessel	6	6	6
Weighted average interest rate				5.01%
New Secured Notes
Debt [Line Items]
Debt instrument fixed interest rate	8.00%	8.00%	8.00%
Aggregate principal amount	$ 350	$ 350	$ 350
Debt instrument maturity date		Dec. 30, 2022
New Secured Notes \| Plan of Reorganization
Debt [Line Items]
Debt instrument maturity date	Aug. 01, 2022
Debt instrument interest term	Interest on the New Secured Notes will accrue at a rate of 8.00% per annum payable quarterly in arrears on February 1, May 1, August 1, and November 1 of each year in cash, beginning November 1, 2017.
Debt instrument frequency of periodic payment of interest	quarterly
Debt Instrument default description	The New Secured Notes have minimum interest coverage requirement (EBITDA/Interest), for which compliance will first be measured for the twelve months ending June 30, 2019. Minimum liquidity requirements and other covenants are set forth in the Indenture. The Indenture also contains certain customary events of default.
Debt instrument collateral description	the New Secured Notes and the guarantees by the Guarantors will be secured by the Collateral (as defined in the Indenture) pursuant to the terms of the Indenture and the related security documents. The Trustee’s liens upon the Collateral and the right of the holders of the New Secured Notes to the benefits and proceeds of the Trustee’s liens on the Collateral will terminate and be discharged in certain circumstances described in the Indenture, including: (i) upon satisfaction and discharge of the Indenture in accordance with the terms thereof; or (ii) as to any Collateral of the company or the Guarantors that is sold, transferred or otherwise disposed of by the company or the Guarantors in a transaction or other circumstance that complies with the terms of the Indenture, at the time of such sale, transfer or other disposition. The company is obligated to offer to holders of the New Secured Notes under the Indenture to repurchase the New Secured Notes at par in amounts of up to 100% of asset sale proceeds depending upon the types of assets sold as defined in the Indenture.
New Secured Notes \| Plan of Reorganization \| Maximum
Debt [Line Items]
Percentage of asset sale proceeds to repurchase notes at par amount	100.00%