Loans and Investments (Details 7) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014 item
Loans and Investments
Total interest reserves	$ 14.3
Number of loans	52
Aggregate unpaid principal balance	$ 743.5

Amount of funds placed into an interest reserve, based on contractual requirements, to cover debt service costs.

No definition available.

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