Loans and Investments - Purchased Credit Deterioration and Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2023 USD ($) item loan	Mar. 31, 2022 USD ($) item	Dec. 31, 2022 USD ($) loan
Loans and Investments
Other loans modification \| item	0	0
Interest reserve	$ 118,000		$ 123,700
Number of loans covered under interest reserve \| loan	479		480
Aggregate UPB covered under interest reserve	$ 7,480,000		$ 7,700,000
Number of loans sold \| loan	4
Unpaid principal balance on loans	$ 217,400
Impairment loss on sale of loans	$ 14,589	$ 1,656

Number of financing receivables that have been modified by troubled debt restructurings.

No definition available.

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

- Definition

Carrying amount as of the balance sheet date pertaining to interest reserve funded to cover debt service costs, based on contractual requirements.

+ References

No definition available.

+ Details

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

- Definition

Number of loans covered under the interest reserve fund.

+ References

No definition available.

+ Details

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

- Definition

Amount of aggregate unpaid principal balance covered under the interest reserve fund.

+ References

No definition available.

+ Details

Name:	abr_InterestReserveUnpaidPrincipalBalance
Namespace Prefix:	abr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Represents the number of loans sold.

+ References

No definition available.

+ Details

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

- Definition

The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13(h))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

+ Details

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

- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(4)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

+ Details

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