Represents information pertaining to the amount of assets, which serve as a collateral.

No definition available.

Name:	abr_AssetsPledgedAsCollateral
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the face value of collateral in default, as defined by the CDO indenture, as well as assets deemed to be a credit risk. Credit risk assets are reported by each of the CDOs and are generally defined as the one that, in the CDO collateral manager's reasonable business judgment, has a significant risk of declining in credit quality or, with a passage of time, becoming a defaulted asset.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of investment grade tranches issued by the entity under collateralized debt obligations.

+ References

No definition available.

+ Details

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

- Definition

Reflects the calculation, as of the balance sheet date, of the average interest rate excluding the effect of swap weighted by the amount of debt outstanding by type or by instrument at that time.

+ References

No definition available.

+ Details

Name:	abr_DebtWeightedAverageInterestRateExcludingSwapEffect
Namespace Prefix:	abr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the calculation as of the balance sheet date of the average interest rate weighted by the amount of debt outstanding, including certain fees and costs.

+ References

No definition available.

+ Details

Name:	abr_DebtWeightedAverageInterestRateIncludingFeesAndCosts
Namespace Prefix:	abr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the carrying value of the mortgage loans that serve as collateral.

+ References

No definition available.

+ Details

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

- Definition

Represents the unpaid principal balance of the mortgage loans that serve as collateral.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

No definition available.

+ Details

Name:	us-gaap_DebtIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the collection, including prepayments, of loans receivable issued for financing of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_SecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=abr_CollateralizedDebtObligationsOneMember
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- Details

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Debt Obligations (Details 2) (USD $)	12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
Debt Obligations (Details 2) (USD $)	Dec. 31, 2014 item	Jan. 19, 2005 item	Dec. 31, 2013	Jan. 11, 2006 item	Dec. 14, 2006 item	Dec. 31, 2010
Debt Obligations
Debt, Carrying Value	$ 331,395,126us-gaap_SecuredDebt		$ 639,622,981us-gaap_SecuredDebt
Collateral Cash, Restricted Cash	218,100,529		54,962,316
Collateralized debt obligations
Debt Obligations
Debt, Face Value	312,071,055		619,553,858			42,800,000
Debt, Carrying Value	331,395,126		639,622,981
Collateral Loans, Unpaid Principal	618,184,291		1,042,692,660
Collateral Loans, Carrying Value	489,742,125		915,290,998
Collateral Cash, Restricted Cash	139,416,831		25,407,559
Collateral-At-Risk	433,880,132		607,184,618
Number of investment grade tranches issued	23
Weighted average note rate (as a percent)	3.13%		2.18%
Weighted average note rate excluding the swap effect (as a percent)	1.07%		0.83%
Weighted average note rate including certain fees and costs (as a percent)	5.26%		3.26%
CDO I debt
Debt Obligations
Debt, Face Value	69,972,159	305,000,000	126,753,077
Debt, Carrying Value	75,402,789		132,399,560
Collateral Loans, Unpaid Principal	222,903,486		284,758,473
Collateral Loans, Carrying Value	174,460,160		237,194,618
Collateral Cash, Restricted Cash	5,232,226		79,986
Collateral-At-Risk	180,691,292		179,466,954
Number of investment grade tranches issued		4
Variable interest rate, description		three-month LIBOR
Variable rate, spread (as a percent)		0.77%
Issuance costs		7,200,000
Weighted average note rate (as a percent)	3.23%		3.12%
Assets serving as collateral		469,000,000
Proceeds received from loan repayments held as collateral	56,800,000		7,200,000
CDO II debt
Debt Obligations
Debt, Face Value	97,906,092		196,046,587	356,000,000
Debt, Carrying Value	103,484,624		201,847,417
Collateral Loans, Unpaid Principal	192,522,685		362,150,693
Collateral Loans, Carrying Value	143,824,571		312,859,875
Collateral Cash, Restricted Cash	69,412,808		1,719,760
Collateral-At-Risk	106,139,494		187,213,841
Number of investment grade tranches issued				9
Variable interest rate, description				three-month LIBOR
Variable rate, spread (as a percent)				0.74%
Issuance costs				6,200,000
Weighted average note rate (as a percent)	6.22%		3.74%
Assets serving as collateral				475,000,000
Proceeds received from loan repayments held as collateral	98,100,000		34,100,000
CDO III debt
Debt Obligations
Debt, Face Value	144,192,804		296,754,194		547,500,000
Debt, Carrying Value	152,507,713		305,376,004
Collateral Loans, Unpaid Principal	202,758,120		395,783,494
Collateral Loans, Carrying Value	171,457,394		365,236,505
Collateral Cash, Restricted Cash	64,771,797		23,607,813
Collateral-At-Risk	147,049,346		240,503,823
Number of investment grade tranches issued					10
Variable interest rate, description					three-month LIBOR
Variable rate, spread (as a percent)					0.44%
Issuance costs					9,700,000
Weighted average note rate (as a percent)	0.98%		0.75%
Assets serving as collateral					500,000,000
Proceeds received from loan repayments held as collateral	152,600,000		120,800,000
Revolving note class
Debt Obligations
Debt, Carrying Value	152,500,000		257,400,000
Revolving note amount	100,000,000
Revolving note facility
Debt Obligations
Commitment fee on the undrawn portion (as a percent)					0.22%
Revolving note amount	$ 1,800,000		$ 48,000,000