Annual report pursuant to Section 13 and 15(d)

Activity Related to Noncontrolling Interests (Detail)

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Activity Related to Noncontrolling Interests (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Noncontrolling Interest [Line Items]    
Balance at end of period $ 7,035 $ 7,979
Noncontrolling Interests
   
Noncontrolling Interest [Line Items]    
Balance at beginning of period 68 66
Acquired noncontrolling interests 5 2
Dividends attributable to noncontrolling interests      
Net income attributable to noncontrolling interests      
Balance at end of period $ 73 $ 68