Concentration Risk (Schedule Of Quantitative Radio Audience Ratings Service And Related Software Licensing Revenue Accounted Aggregate Percentages Of Total Company Revenue) (Details)	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Concentration Risk [Abstract]
Quantitative radio audience ratings service and related software licensing revenue	96.00%	96.00%

Quantitative radio audience ratings and related software licensing to total revenue, percentage.

No definition available.

Name:	arb_QuantitativeRadioAudienceRatingsAndRelatedSoftwareLicensingToTotalRevenuePercentage
Namespace Prefix:	arb_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration