SCHEDULE IV - LOANS AND OTHER LENDING INVESTMENTS (Details) $ in Thousands	12 Months Ended
Dec. 31, 2024 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 2,291,951
Carrying value of loans	11,304,956
Carrying Amount	11,033,997
Carrying Amount Subject to Delinquent Interest	0
Amount of loans extended	5,990,000
Federal income tax basis	$ 11,300,000
Threshold for reporting loans (as a percent)	3.00%
Bridge Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Carrying value of loans	10,893,106
Carrying Amount	10,652,225
Carrying Amount Subject to Delinquent Interest	0
Mezzanine Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	1,335,133
Carrying value of loans	255,556
Carrying Amount	234,749
Carrying Amount Subject to Delinquent Interest	0
Preferred Equity Investments \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	956,818
Carrying value of loans	148,845
Carrying Amount	140,414
Carrying Amount Subject to Delinquent Interest	0
Other Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Carrying value of loans	7,449
Carrying Amount	6,609
Carrying Amount Subject to Delinquent Interest	0
Multifamily \| Bridge Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Carrying value of loans	8,725,429
Carrying Amount	8,588,684
Carrying Amount Subject to Delinquent Interest	$ 0
Multifamily \| Bridge Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	(0.0125)
Floor rate (as a percent)	0.10%
Fixed interest rate (as a percent)	0.00%
Multifamily \| Bridge Loans \| Loans less than 3% \| Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0575
Floor rate (as a percent)	5.36%
Fixed interest rate (as a percent)	11.00%
Multifamily \| Mezzanine Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 1,335,133
Carrying value of loans	239,203
Carrying Amount	221,689
Carrying Amount Subject to Delinquent Interest	$ 0
Multifamily \| Mezzanine Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	0.00%
Multifamily \| Mezzanine Loans \| Loans less than 3% \| Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	14.00%
Multifamily \| Preferred Equity Investments \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 927,026
Carrying value of loans	143,645
Carrying Amount	137,163
Carrying Amount Subject to Delinquent Interest	$ 0
Multifamily \| Preferred Equity Investments \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	0.00%
Multifamily \| Preferred Equity Investments \| Loans less than 3% \| Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	16.00%
Multifamily \| Other Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Floor rate (as a percent)	4.00%
Fixed interest rate (as a percent)	4.25%
Prior Liens	$ 0
Carrying value of loans	4,367
Carrying Amount	3,531
Carrying Amount Subject to Delinquent Interest	$ 0
Multifamily \| Other Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0550
Single‑Family Rental \| Bridge Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	$ 0
Carrying value of loans	1,993,890
Carrying Amount	1,967,835
Carrying Amount Subject to Delinquent Interest	$ 0
Single‑Family Rental \| Bridge Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0295
Floor rate (as a percent)	0.10%
Single‑Family Rental \| Bridge Loans \| Loans less than 3% \| Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0620
Floor rate (as a percent)	5.36%
Single‑Family Rental \| Other Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Floor rate (as a percent)	0.25%
Prior Liens	$ 0
Carrying value of loans	3,082
Carrying Amount	3,078
Carrying Amount Subject to Delinquent Interest	$ 0
Single‑Family Rental \| Other Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0490
Land \| Bridge Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0400
Floor rate (as a percent)	0.15%
Fixed interest rate (as a percent)	13.00%
Prior Liens	$ 0
Carrying value of loans	125,877
Carrying Amount	47,977
Carrying Amount Subject to Delinquent Interest	$ 0
Land \| Mezzanine Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	0.00%
Prior Liens	$ 0
Carrying value of loans	9,333
Carrying Amount	9,333
Carrying Amount Subject to Delinquent Interest	$ 0
Land \| Preferred Equity Investments \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	0.00%
Prior Liens	$ 0
Carrying value of loans	3,500
Carrying Amount	3,251
Carrying Amount Subject to Delinquent Interest	$ 0
Office \| Bridge Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0350
Prior Liens	$ 0
Carrying value of loans	35,410
Carrying Amount	35,229
Carrying Amount Subject to Delinquent Interest	0
Retail \| Bridge Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Prior Liens	0
Carrying value of loans	12,500
Carrying Amount	12,500
Carrying Amount Subject to Delinquent Interest	$ 0
Retail \| Bridge Loans \| Loans less than 3% \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0350
Floor rate (as a percent)	1.00%
Retail \| Mezzanine Loans \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Financing receivable, basis spread on variable rate	0.0350
Floor rate (as a percent)	1.00%
Fixed interest rate (as a percent)	0.00%
Prior Liens	$ 0
Carrying value of loans	7,020
Carrying Amount	3,727
Carrying Amount Subject to Delinquent Interest	$ 0
Commercial \| Preferred Equity Investments \| Loans less than 3%
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fixed interest rate (as a percent)	6.00%
Prior Liens	$ 29,792
Carrying value of loans	1,700
Carrying Amount	0
Carrying Amount Subject to Delinquent Interest	$ 0

Financing Receivable, Basis Spread On Variable Rate

No definition available.

Name:	abr_FinancingReceivableBasisSpreadOnVariableRate
Namespace Prefix:	abr_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value of loans derived after deducting unearned revenue and other holdbacks.

+ References

No definition available.

+ Details

Name:	abr_LoanCarryingValue
Namespace Prefix:	abr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the minimum LIBOR rate on the loans receivable.

+ References

No definition available.

+ Details

Name:	abr_LoansReceivableFloorRate
Namespace Prefix:	abr_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The threshold percentage for reporting loans in the schedule of mortgage loans on real estate.

+ References

No definition available.

+ Details

Name:	abr_ThresholdPercentageForReportingLoans
Namespace Prefix:	abr_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of federal income tax basis of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 29
-Paragraph Column G
-Footnote 8
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 8))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	srt_MortgageLoansOnRealEstateFederalIncomeTaxBasis1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Interest rate of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 29
-Paragraph Column B
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	srt_MortgageLoansOnRealEstateInterestRate
Namespace Prefix:	srt_
Data Type:	dtr-types:percentItemType
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 29
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	srt_MortgageLoansOnRealEstateLineItems
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of principal due on delinquent mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 29
-Paragraph Column H
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column H))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	srt_MortgageLoansOnRealEstatePrincipalAmountOfDelinquentLoans
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of prior lien on real estate securing mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 29
-Paragraph Column E
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column E))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	srt_MortgageLoansOnRealEstatePriorLiens1
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

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

- Definition

Amount of mortgage loan in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, renewed or extended.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

Name:	us-gaap_MortgageLoansOnRealEstateRenewedAndExtendedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_BridgeLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=abr_MezzanineLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=abr_LoansLessThanThreePercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=abr_PreferredEquityInvestmentsInMortgageLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=abr_OtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=abr_RealEstateSingleFamilyRentalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_LandAndLandImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_OfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_RetailSiteMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: