Quantitative Radio Audience Ratings Service and Related Software Licensing Revenue Accounted Aggregate Percentages of Total Company Revenue (Detail)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Concentration Risk [Abstract]
Quantitative radio audience ratings service and related software licensing revenue	95.00%	96.00%

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

No definition available.

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Balance Type:	na
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