Organization, Consolidation and Presentation of Financial Statements - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended	12 Months Ended
	Aug. 15, 2012	Sep. 30, 2012 Segment	Dec. 31, 2011	Dec. 30, 2011
Number of operating business segments		2
Number of conference calls managed by company			121,000,000
Percentage increase in conference calls over 2010			13.00%
cash dividend declared	$ 1.00
cash dividend payable date		Aug. 15, 2012
Conversion of one class L common stock into class A common stock			40.29
Common stock, shares authorized		1,000,000,000	1,000,000,000	1,000,000,000
Common Class A [Member]
Common stock, shares authorized				900,000,000
Class L Common Stock
Common stock, shares authorized				100,000,000