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 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Stockholders Equity Note [Roll Forward]        
Common stock purchases     (21.8) (11.3)
Balance at beginning of period     $ 4,653  
Net income 1,071 1,116 2,108 2,086
Common stock purchases     (1,836) (870)
Balance at end of period 3,617   3,617  
Class A common stock
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period       240
Common stock purchases     (4.0) (3.0)
Stock award plans     5 4
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures     0 0
Common stock issuances     2 2
Conversions of Class A to Class B common stock     (10) (8)
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 218 235 218 235
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     (18.0) (8.0)
Conversions of Class A to Class B common stock     10 8
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 721 725 721 725
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     364 291
Common stock issuances     149 144
Option premiums received (paid)     (399) 206
Common stock purchases     (114) (606)
Balance at end of period 0 0 0 0
StockRepurchaseProgramRepurchaseAmountUnsettled 0 (35) 0 (35)
Retained Earnings
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     7,997 10,128
Net income     2,108 2,086
Dividends ($0.57 and $0.52 per share)     (1,199) (1,123)
Common stock purchases     (1,721) (264)
Balance at end of period $ 7,185 $ 10,827 $ 7,185 $ 10,827
Common stock, cash paid for dividends, per share $ 1.24 $ 1.14