Quarterly report pursuant to Section 13 or 15(d)

Roll-forward of Common Stock, Additional Paid-in Capital, and Retained Earnings Accounts (Detail)

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Roll-forward of Common Stock, Additional Paid-in Capital, and Retained Earnings Accounts (Detail) (USD $)
In Millions, except Per Share data, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Stockholders Equity Note [Roll Forward]        
Common stock purchases     (33.3) (18.5)
Balance at beginning of period     $ 4,653  
Net income 1,097 469 3,205 2,555
Common stock purchases     (2,844) (1,392)
Balance at end of period 3,642   3,642  
Class A common stock
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period       240
Common stock purchases     (6.0) (6.0)
Stock award plans     6 5
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures     0 0
Common stock issuances     3 3
Conversions of Class A to Class B common stock     (14) (11)
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 214 231 214 231
Balance at beginning of period     3 3
Common stock issuances     0 0
Common stock purchases     (1) 0
Balance at end of period 2 3 2 3
Class B common stock
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period       725
Common stock purchases     (27.0) (13.0)
Conversions of Class A to Class B common stock     14 11
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 716 723 716 723
Balance at beginning of period     7 7
Common stock purchases     0 0
Balance at end of period 7 7 7 7
Additional Paid-in Capital
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     0 0
Stock award plans     493 414
Common stock issuances     216 207
Option premiums received (paid)     (196) 206
Common stock purchases     (513) (827)
Balance at end of period 0 0 0 0
Retained Earnings
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     7,997 10,128
Net income     3,205 2,555
Dividends ($0.57 and $0.52 per share)     (1,770) (1,670)
Common stock purchases     (2,330) (565)
Balance at end of period $ 7,102 $ 10,448 $ 7,102 $ 10,448
Common stock, cash paid for dividends, per share     $ 1.86 $ 1.71