Arbitron Mobile Contingent Consideration - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Y	Jul. 28, 2011	Mar. 31, 2013 Noncurrent Liabilities	Dec. 31, 2012 Noncurrent Liabilities	Mar. 31, 2013 Maximum
Business Acquisition, Contingent Consideration [Line Items]
Business acquisition, cash paid		$ 10.6
Fair value of contingent consideration			0.6	0.6
Potential cash payment to shareholders					$ 12.0
Contingent consideration expiration year	2015
Period for performance evaluation, years	4
Business acquisition, effective date	Jul. 28, 2011