DEBT (Subordinate Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Net premium and debt issue costs	$ 7,337
Carrying Value	$ 201,816	$ 149,187
Subordinated principal (as percent)	2.00%
Subordinated Loan [Member] \| MMA Financial Holdings Inc. Debt [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 88,045
Net premium and debt issue costs	7,443
Carrying Value	95,488
Subordinated Loan [Member] \| MFH Issue 1 [Member]
Debt Instrument [Line Items]
Principal amount of debt	25,999
Net premium and debt issue costs	2,264
Carrying Value	$ 28,263
Maturity Date	March 30, 2035
Coupon Interest Rate	three-month LIBOR plus 2.0%
Subordinated Loan [Member] \| MFH Issue 2 [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 23,641
Net premium and debt issue costs	2,070
Carrying Value	$ 25,711
Maturity Date	April 30, 2035
Coupon Interest Rate	three-month LIBOR plus 2.0%
Subordinated Loan [Member] \| MFH Issue 3 [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 13,628
Net premium and debt issue costs	1,103
Carrying Value	$ 14,731
Maturity Date	July 30, 2035
Coupon Interest Rate	three-month LIBOR plus 2.0%
Subordinated Loan [Member] \| MFH Issue 4 [Member]
Debt Instrument [Line Items]
Principal amount of debt	$ 24,777
Net premium and debt issue costs	2,006
Carrying Value	$ 26,783
Maturity Date	July 30, 2035
Coupon Interest Rate	three-month LIBOR plus 2.0%

Represents the principal amortization percent of debt instrument.

No definition available.

Name:	mmac_DebtInstrumentPrincipalAmortizationPercent
Namespace Prefix:	mmac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Principal Amount

+ References

No definition available.

+ Details

Name:	mmac_DebtInstrumentPrincipalAmount
Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of debt discount (net of debt premium) and debt issuance cost that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

No definition available.

+ Details

Name:	mmac_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostNet
Namespace Prefix:	mmac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- 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

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ 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 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: 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(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=mmac_MmaFinancialHoldingsInc.DebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mmac_MfhIssue1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mmac_MfhIssue2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mmac_MfhIssue3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mmac_MfhIssue4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: