Quantitative Radio Audience Ratings Service and Related Software Licensing Revenue Accounted Aggregate Percentages of Total Company Revenue (Detail)	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Concentration Risk [Abstract]
Quantitative radio audience ratings service and related software licensing revenue	94.00%	95.00%	91.00%	91.00%

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

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