No definition available.

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Namespace Prefix:	mrc_
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- Definition

The total of the cash outflow during the period which has been paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt and the cost incurred directly for the issuance of equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3291-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the additional capital contribution to the entity.

+ 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 (a)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

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Balance Type:	debit
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- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=mrc_DRIPMember
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SHARE OFFERINGS AND FEES (Details) - USD ($)		6 Months Ended	12 Months Ended
SHARE OFFERINGS AND FEES (Details) - USD ($)	Oct. 31, 2020	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Sale of Stock [Abstract]
Shares issued (in shares)	504,091.15		21,720	1,943,646
Proceeds from shares issued		$ 218,439	$ 218,439	$ 19,505,452	$ 23,244,171
Payments of selling commissions and fees			$ 18,060	$ 1,823,648
Price per share (in dollars per share)	$ 7.85		$ 10.00
DRIP [Member]
Sale of Stock [Abstract]
Shares issued (in shares)				317,840
Proceeds from shares issued				$ 2,891,349
Payments of selling commissions and fees				$ 0