Debt instrument maturity year.

No definition available.

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

- Definition

Debt instrument repurchase period.

+ References

No definition available.

+ Details

Name:	tdw_DebtInstrumentRepurchasePeriod
Namespace Prefix:	tdw_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

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

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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13476-108611

+ Details

Name:	us-gaap_DebtInstrumentFairValue
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

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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

- 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

Fair value amount of debt instrument that was repurchased.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentRepurchaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=tdw_EightPointZeroZeroPercentNewSecuredNotesDueAugustTwoThousandTwentyTwoMember
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:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	5 Months Ended	9 Months Ended
	Jul. 31, 2017	Jul. 31, 2017	Dec. 31, 2017	Dec. 31, 2017
Debt [Line Items]
Aggregate principal amount	$ 350,000	$ 350,000
Debt instrument maturity year	2022
Net proceeds of each qualified asset sale			$ 32,742
8.00% New Secured Notes Due August 2022
Debt [Line Items]
Debt instrument interest rate	8.00%	8.00%	8.00%	8.00%
Aggregate principal amount	$ 350,000	$ 350,000
Debt instrument maturity year		2022
8.00% New Secured Notes Due August 2022 \| 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 and are in effect from July 31, 2017. The Indenture also contains certain customary events of default and a make-whole provision.
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 repurchase the New Secured Notes at par in amounts that generally approximate 65% of asset sale proceeds depending upon the types of assets sold as defined in the Indenture. The company maintains a restricted cash account to accumulate the net proceeds of each qualified asset sale, which account had a balance of $21.3 million at December 31, 2017. In the event the holders of the New Secured Notes do not accept the company’s offer to repurchase the notes the accumulated cash would become available to the company for its general use.
Percentage of asset sale proceeds to repurchase notes at par amount	65.00%
Net proceeds of each qualified asset sale				$ 21,300
Debt instrument repurchase period	60 days
Debt instrument repurchase accumulation amount	$ 10	$ 10
8.00% New Secured Notes Due August 2022 \| Plan of Reorganization \| Level 2
Debt [Line Items]
Fair value in U.S. dollar equivalent			$ 359,800	$ 359,800