Debt Instrument Amortization Percentage

No definition available.

Name:	mrc_DebtInstrumentAmortizationPercentage
Namespace Prefix:	mrc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Extinguishment of Debt, Cost

+ References

No definition available.

+ Details

Name:	mrc_ExtinguishmentOfDebtCost
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage Of Capital Stock In Foreign Subsidiaries

+ References

No definition available.

+ Details

Name:	mrc_PercentageOfCapitalStockInForeignSubsidiaries
Namespace Prefix:	mrc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Repayment percentage requirement based on excess cash flow and leverage ratio.

+ References

No definition available.

+ Details

Name:	mrc_RepaymentPercentageRequirementBasedOnExcessCashFlowAndLeverageRatio
Namespace Prefix:	mrc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate amount of incremental increases allowed under the Senior Secured Term Loan.

+ References

No definition available.

+ Details

Name:	mrc_SeniorSecuredTermLoanMaximumBorrowingCapacity
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Term Loan Senior Secured Leverage Ratio

+ References

No definition available.

+ Details

Name:	mrc_TermLoanSeniorSecuredLeverageRatio
Namespace Prefix:	mrc_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

Reference 2: 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.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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

- Details

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

- Details

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

- Details

Name:	srt_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_GB
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_AU
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_BE
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_NO
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_NL
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended
Long-Term Debt (Narrative) (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Proceeds from revolving credit facilities		$ 205,000,000	$ 319,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Debt returned	$ 3,000,000
Cost of extinguishment	2,000,000
Gain on extinguishment of debt	1,000,000
Global ABL Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	800,000,000	800,000,000
Credit facility, remaining borrowing capacity	437,000,000	437,000,000
Proceeds from revolving credit facilities		200,000,000
Global ABL Facility [Member] \| United States [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	675,000,000	675,000,000
Global ABL Facility [Member] \| Canada [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	65,000,000	65,000,000
Global ABL Facility [Member] \| United Kingdom [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	7,000,000	7,000,000
Global ABL Facility [Member] \| Australia [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	15,000,000	15,000,000
Global ABL Facility [Member] \| Belgium [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	7,000,000	7,000,000
Global ABL Facility [Member] \| Norway [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	18,000,000	18,000,000
Global ABL Facility [Member] \| Netherlands [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	13,000,000	13,000,000
Secured Term Loan [Member] \| Senior Secured Term Loan B [Member]
Debt Instrument [Line Items]
Principal amount	400,000,000	$ 400,000,000
Term loan annual amortization percentage		1.00%
Term Loan accordion feature	$ 200,000,000	$ 200,000,000
Percentage of capital stock in foreign subsidiaries securing Term Loan B		65.00%
Secured Term Loan [Member] \| Senior Secured Term Loan B [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Variable interest rate		2.00%
Secured Term Loan [Member] \| Senior Secured Term Loan B [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable interest rate		3.00%
Secured Term Loan [Member] \| Senior Secured Leverage Ratio Is No More Than 2.75 to 1.00 [Member] \| Senior Secured Term Loan B [Member]
Debt Instrument [Line Items]
Senior secured leverage ratio		2.75
Repayment of Term Loan, percentage		25.00%
Secured Term Loan [Member] \| Senior Secured Leverage Ratio Is No More Than 2.50 to 1.00 [Member] \| Senior Secured Term Loan B [Member]
Debt Instrument [Line Items]
Senior secured leverage ratio		2.50
Secured Term Loan [Member] \| Maximum [Member] \| Senior Secured Term Loan B [Member]
Debt Instrument [Line Items]
Senior secured leverage ratio		4.00
Repayment of Term Loan, percentage		50.00%