Debt instrument maturity year.

No definition available.

Name:	mdr_DebtInstrumentMaturityYear
Namespace Prefix:	mdr_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt instrument scheduled interest payment due.

+ References

No definition available.

+ Details

Name:	mdr_DebtInstrumentScheduledInterestPaymentDue
Namespace Prefix:	mdr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of credit facility available for capital.

+ References

No definition available.

+ Details

Name:	mdr_LineOfCreditFacilityAvailableForCapital
Namespace Prefix:	mdr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum percentage of aggregate principle amount called up for immediate repayment upon default of scheduled interest payment.

+ References

No definition available.

+ Details

Name:	mdr_MinimumPercentageOfAggregatePrincipleAmountCalledUpForImmediateRepaymentUponDefaultOfScheduledInterestPayment
Namespace Prefix:	mdr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mdr_TrancheAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mdr_TrancheBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=mdr_AvailableToBorrowersBetweenNovemberThirtyTwoThousandNineteenAndDecemberThirtyFirstTwoThousandNineteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mdr_TrancheCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=mdr_AvailableToBorrowersBetweenDecemberThirtyTwoThousandNineteenAndMarchThirtyFirstTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=mdr_TrancheDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=mdr_AvailableToBorrowersBetweenJanuaryThirtyFirstTwoThousandTwentyAndMarchThirtyFirstTwoThousandTwentyMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=mdr_NewTermFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] - USD ($)	Nov. 01, 2019	Oct. 21, 2019
Senior Notes [Member]
Subsequent Event [Line Items]
Scheduled interest payment due	$ 69,000,000
Debt Instrument maturity year	2024
Minimum percentage of aggregate principle amount called up for immediate repayment upon default of scheduled interest payment	25.00%
Superpriority Credit Agreement [Member]
Subsequent Event [Line Items]
Available capacity under credit facility		$ 1,700,000,000
Line of credit facility, expiration date		Oct. 21, 2021
Superpriority Credit Agreement [Member] \| Tranche A [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		$ 650,000,000
Superpriority Credit Agreement [Member] \| Tranche B [Member] \| Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		350,000,000
Superpriority Credit Agreement [Member] \| Tranche C [Member] \| Available to Borrowers between December 30, 2019 and March 31, 2020 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		150,000,000
Superpriority Credit Agreement [Member] \| Tranche D [Member] \| Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		550,000,000
Superpriority Credit Agreement [Member] \| New LC Facility [Member]
Subsequent Event [Line Items]
Available capacity under credit facility		400,000,000
Superpriority Credit Agreement [Member] \| New LC Facility [Member] \| Tranche A [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		100,000,000
Superpriority Credit Agreement [Member] \| New LC Facility [Member] \| Tranche B [Member] \| Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		100,000,000
Superpriority Credit Agreement [Member] \| New LC Facility [Member] \| Tranche D [Member] \| Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		200,000,000
Superpriority Credit Agreement [Member] \| New Term Facility [Member]
Subsequent Event [Line Items]
Available capacity under credit facility		1,300,000,000
Superpriority Credit Agreement [Member] \| New Term Facility [Member] \| Tranche A [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		550,000,000
Superpriority Credit Agreement [Member] \| New Term Facility [Member] \| Tranche B [Member] \| Available to Borrowers between November 30, 2019 and December 31, 2019 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		250,000,000
Superpriority Credit Agreement [Member] \| New Term Facility [Member] \| Tranche D [Member] \| Available to Borrowers between January 31, 2020 and March 31, 2020 [Member]
Subsequent Event [Line Items]
Line of credit facility available for capital		$ 350,000,000