Quantitative Radio Audience Ratings Service and Related Software Licensing Revenue Accounted Aggregate Percentages of Total Company Revenue (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Concentration Risk
Quantitative radio audience ratings service and related software licensing revenue	81.00%	82.00%	88.00%	89.00%