Residential Whole Loans - Vintage Information Regarding Residential Whole Loans (Details) - Residential whole loan - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Business purpose loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 4,017,444	$ 3,996,292
Business purpose loans \| Multifamily transitional loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,155,198	1,168,297
Business purpose loans \| Single-family rental loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,643,690	1,634,796
Non-QM loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3,995,591	3,805,577
Legacy RPL/NPL loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	1,133,056	1,204,095
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	53,416	55,779
Estimated Fair Value
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	1,001,104
2023	2,291,526
2022	1,797,885
2021	1,981,047
2020	9,446
Prior	691,599
Total	7,772,607
Estimated Fair Value \| Business purpose loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	3,860,116	3,788,612
Estimated Fair Value \| Business purpose loans \| Single-family transitional loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	317,005
2023	618,208
2022	224,974
2021	29,773
2020	398
Prior	341
Total	1,190,699
Estimated Fair Value \| Business purpose loans \| Multifamily transitional loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	94,417
2023	548,950
2022	365,969
2021	145,862
2020	0
Prior	0
Total	1,155,198	1,168,297
Estimated Fair Value \| Business purpose loans \| Single-family rental loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	185,993
2023	360,847
2022	573,014
2021	385,268
2020	8,820
Prior	277
Total	1,514,219	1,462,583
Estimated Fair Value \| Non-QM loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	403,689
2023	763,521
2022	633,928
2021	1,366,728
2020	228
Prior	35,751
Total	3,203,845	2,961,693
Estimated Fair Value \| Legacy RPL/NPL loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	0
2023	0
2022	0
2021	0
2020	0
Prior	655,230
Total	655,230	705,424
Estimated Fair Value \| Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
2024	0
2023	0
2022	0
2021	53,416
2020	0
Prior	0
Total	$ 53,416	$ 55,779

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481628/310-20-40-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-2

+ Details

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

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mfa_BusinessPurposeLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=mfa_MultiFamilyTransitionalLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=mfa_SingleFamilyRentalLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mfa_NonQMLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mfa_LegacyReperformingAndNonPerformingLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=mfa_OtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=mfa_SingleFamilyTransitionalLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: