STOCKHOLDER DIVIDENDS (Details) - USD ($)	3 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Dividends Declared [Abstract]
Common dividends	$ 1,586,864	$ 1,323,888
Preferred dividends	242,173	37,980
Preferred Stock Units [Member]
Dividends Declared [Abstract]
Dividends, Preferred stock		51,667
Preferred dividends	177,589
Class A [Member]
Dividends Declared [Abstract]
Common dividends	$ 10,229	$ 6,299
Dividend Declared Q1-2024 [Member]
Dividends Declared [Abstract]
Dividends declaration date	Sep. 30, 2023
Dividends, Common stock	$ 1,652,688
Dividends, Preferred stock	$ 268,383
Dividend Declared Q1-2024 [Member] \| Common Stock [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)	$ 0.125
Dividend Declared Q1-2024 [Member] \| Preferred Stock [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)	0.375
Dividends Payable, Monthly amount Per Share	0.125
Dividend Declared Q1-2024 [Member] \| Preferred Stock Units [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)	$ 0.375
Dividends, Preferred stock	$ 177,930
Dividend Declared Q1-2024 [Member] \| Class A [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)	$ 0.125
Dividends, Common stock	$ 10,372
Dividend Declared Q1-2023 [Member]
Dividends Declared [Abstract]
Dividends declaration date		Sep. 30, 2022
Dividends, Common stock		$ 1,390,290
Dividends, Preferred stock		$ 87,884
Dividend Declared Q1-2023 [Member] \| Common Stock [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)		$ 0.105
Dividend Declared Q1-2023 [Member] \| Preferred Stock [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)		0.375
Dividend Declared Q1-2023 [Member] \| Preferred Stock Units [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)		$ 0.375
Dividends, Preferred stock		$ 107,626
Dividend Declared Q1-2023 [Member] \| Class A [Member]
Dividends Declared [Abstract]
Dividends per share (in dollars per share)		$ 0.105
Dividends, Common stock		$ 9,324
DRIP [Member]
Dividends Declared [Abstract]
Dividends, Common stock	443,271	386,385
Dividends, Preferred stock	39,858	$ 4,829
DRIP [Member] \| Preferred Stock Units [Member]
Dividends Declared [Abstract]
Dividends, Preferred stock	$ 20,454

No definition available.

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

- Definition

The monthly amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

No definition available.

+ Details

Name:	mrc_DividendsPayableAmountPerSharePerMonth
Namespace Prefix:	mrc_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-SubTopic 405
-Topic 942
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481071/942-405-45-2

+ Details

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

- Definition

Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

+ References

+ Details

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

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-3

+ Details

Name:	us-gaap_DividendsPayableAmountPerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the dividend to be paid was declared, in YYYY-MM-DD format.

+ References

+ Details

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

- Definition

Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

+ References

+ Details

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

- Definition

Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash.

+ References

+ Details

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

- Details

Name:	us-gaap_StatementEquityComponentsAxis=mrc_PreferredStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_CommonClassAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DividendsAxis=mrc_DividendDeclared2024Q1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_PreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DividendsAxis=mrc_DividendDeclared2023Q1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DividendsAxis=mrc_DRIPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: