Name:	abr_ContractualObligations
Namespace Prefix:	abr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Funded and unfunded amount, before allowance for credit loss, of financing receivable.

No definition available.

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

- References

No definition available.

Name:	abr_LoanSalesDataAbstract
Namespace Prefix:	abr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of loans originated during the period.

No definition available.

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

Amount of loans originated through loan payoffs and paydowns.

No definition available.

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

Amount of new loans originated during the period

No definition available.

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

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

No definition available.

Name:	abr_NumberOfLoansUnderSpecifiedLoanPortfolio
Namespace Prefix:	abr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Originated mortgage servicing rights rate, MSR income as a percent of loan commitments.

No definition available.

Name:	abr_OriginatedMortgageServicingRightsRate
Namespace Prefix:	abr_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Sale margin as a percent of loan sales.

No definition available.

Name:	abr_SaleMarginOfMortgageLoanSold
Namespace Prefix:	abr_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

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

The cash inflow from sales of loans that are secured with real estate mortgages and are held with the intention to resell in the near future.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3461-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3536-108585

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

Name:	us-gaap_StatementBusinessSegmentsAxis=abr_StructuredTransactionBusinessSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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

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

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

Name:	us-gaap_StatementBusinessSegmentsAxis=abr_AgencyBusinessSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

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

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