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Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

This item represents increase (decrease) in the fair value of bonds.

No definition available.

Name:	mmac_IncreaseDecreaseInFairValueOfBonds
Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The carrying value of bonds on non-accrual as of the balance sheet date.

No definition available.

Name:	mmac_NonAccrualBonds
Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Reflects the amount of interest income recognized using a cash-basis method during the period from nonaccrual bonds.

No definition available.

Name:	mmac_NonAccrualBondsInterestIncomeCashBasisMethod
Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the number of municipal bonds.

No definition available.

Name:	mmac_NumberOfMunicipalBonds
Namespace Prefix:	mmac_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 230
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

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

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.

No definition available.

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

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancialInstrumentAxis=mmac_InfrastructureBondMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancialInstrumentAxis=mmac_MultifamilyTaxExemptBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: