Summary of Significant Accounting Policies (Details)	6 Months Ended
Jun. 30, 2014 item
Summary of Significant Accounting Policies
Number of collateralized debt obligation subsidiaries	3
Number of collateralized loan obligation subsidiaries	3

Represents the number of collateralized debt obligation subsidiaries in which the entity is a primary beneficiary.

No definition available.

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