Amount of financing receivable past due.

No definition available.

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

- Definition

Amount of loans, net carrying value.

+ References

No definition available.

+ Details

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

- Definition

The amount of net loss of swaps gain with loans.

+ References

No definition available.

+ Details

Name:	abr_NetLossOfSwapsGainWithLoans
Namespace Prefix:	abr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the number of loans related to the real estate property under the loan portfolio.

+ References

No definition available.

+ Details

Name:	abr_NumberOfLoansUnderLoanPortfolio
Namespace Prefix:	abr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum period from the origination date a loan receivables held-for-sale will be sold.

+ References

No definition available.

+ Details

Name:	abr_PeriodOfLoansHeldForSaleSold
Namespace Prefix:	abr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow resulting from the sale of loans excluding loans acquired which are classified as held-for-sale, including proceeds from loans sold through mortgage securitization.

+ References

No definition available.

+ Details

Name:	abr_ProceedsFromSaleOfLoansHeldForSaleExcludingAcquisition
Namespace Prefix:	abr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of upb is unpaid principal balance.

+ References

No definition available.

+ Details

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

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

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

+ Details

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

- Definition

Amount of gain (loss) on sale of financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481326/860-20-50-5

+ Details

Name:	us-gaap_GainLossOnSaleOfNotesReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=us-gaap_UsGovernmentSponsoredEnterpriseInsuredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=abr_PrivateLabelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans Held-for-Sale, Net - Narrative (Details)	3 Months Ended		12 Months Ended
Loans Held-for-Sale, Net - Narrative (Details)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) loan	Dec. 31, 2023 USD ($)
Loans Held-for-Sale, Net
Sale of loans held-for-sale excluding acquired loans	$ 1,090,000,000.00	$ 932,700,000
Loans held-for-sale placed on non-accrual status	0			$ 0
Greater Than 90 Days Past Due
Loans Held-for-Sale, Net
Loans held-for-sale that were 90 days or more past due	$ 0			$ 0
US Government Sponsored-Enterprise Insured Loans
Loans Held-for-Sale, Net
Period of loans held for sale sold	60 days
Private Label
Loans Held-for-Sale, Net
Period of loans held for sale sold	180 days
Net loss of swaps gain with loans			$ 5,200,000
Number of loans under the loan portfolio \| loan			7
Unpaid principal balance			$ 129,900,000
Net loans carrying value			$ 116,400,000
Gain on sale of loans		$ 900,000