Quarterly report pursuant to Section 13 or 15(d)

Activity Related to Noncontrolling Interests (Detail)

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Activity Related to Noncontrolling Interests (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]    
Balance at beginning of period $ 73 $ 68
Acquired noncontrolling interests 12 3
Dividends attributable to noncontrolling interests 0 0
Net income attributable to noncontrolling interests 0 0
Balance at end of period $ 85 $ 71