Number of Shares of Class A Common Shares Outstanding on an As-Converted Basis (Detail) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011	Dec. 29, 2011	Sep. 30, 2011
Schedule of Common Stock as Converted [Line Items]
Shares Outstanding As Converted Basis	670	[1]
Class A common stock
Schedule of Common Stock as Converted [Line Items]
Shares Outstanding	527				520
Conversion Rate Into Class A Common Stock
Shares Outstanding As Converted Basis	527	[1]
Class B common stock
Schedule of Common Stock as Converted [Line Items]
Shares Outstanding	245				245
Conversion Rate Into Class A Common Stock	0.4254			0.4254
Shares Outstanding As Converted Basis	104	[1]	104
Class C common stock
Schedule of Common Stock as Converted [Line Items]
Shares Outstanding	38				47
Conversion Rate Into Class A Common Stock	1.0000
Shares Outstanding As Converted Basis	38	[1]

[1] Figures may not sum due to rounding. As-converted class A common stock count calculated based on whole numbers.