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

Amount classified as allowance for impairment of assets held for sale attributable to disposal group held for sale or disposed of.

No definition available.

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

Amount classified as building, fixtures and improvements attributable to disposal group held for sale or disposed of.

No definition available.

Name:	mrc_DisposalGroupIncludingDiscontinuedOperationBuildingFixturesAndImprovements
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount classified as deferred rent and other liabilities attributable to disposal group held for sale or disposed of.

No definition available.

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

Amount classified as due from related entities attributable to disposal group held for sale or disposed of.

No definition available.

Name:	mrc_DisposalGroupIncludingDiscontinuedOperationDueFromRelatedEntities
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount classified as lease intangible assets attributable to disposal group held for sale or disposed of.

No definition available.

Name:	mrc_DisposalGroupIncludingDiscontinuedOperationIntangibleLeaseAssets
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount classified as investments income, rents and other receivables attributable to disposal group held for sale or disposed of.

No definition available.

Name:	mrc_DisposalGroupIncludingDiscontinuedOperationInvestmentsIncomeRentsAndOtherReceivables
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount classified as land attributable to disposal group held for sale or disposed of.

No definition available.

Name:	mrc_DisposalGroupIncludingDiscontinuedOperationLand
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of gain (loss) on disposal of real estate.

No definition available.

Name:	mrc_GainLossOnDisposalOfRealEstate
Namespace Prefix:	mrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

Name:	mrc_RealEstateAssetsAbstract
Namespace Prefix:	mrc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of net sale of closing costs.

No definition available.

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

Amount classified as assets attributable to disposal group held for sale or disposed of.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-SubTopic 20
-Topic 205
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483475/205-20-45-10

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5C
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-5C

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5B
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-5B

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482099/360-10-50-3

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483475/205-20-45-11

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

Amount classified as accounts payable and accrued liabilities attributable to disposal group held for sale or disposed of.

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

Amount classified as cash and cash equivalents attributable to disposal group held for sale or disposed of.

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

Amount classified as prepaid and other assets attributable to disposal group held for sale or disposed of.

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

Amount classified as property, plant and equipment attributable to disposal group held for sale or disposed of.

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

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482130/360-10-45-15

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

- References

No definition available.

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

Amount classified as liabilities attributable to disposal group held for sale or disposed of.

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

- References

No definition available.

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

Cash received for the sale of real estate that is not part of an investing activity during the current period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-12