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, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Stockholders Equity Note [Roll Forward]        
Common stock purchases     (13.7) (21.8)
Balance at beginning of period     $ 6,474  
Net income 454 1,071 1,365 2,108
Common stock purchases     (1,363) (1,836)
Balance at end of period 5,568   5,568  
Class A common stock
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     212 225
Common stock purchases     (3.0) (4.0)
Stock award plans     4 5
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures     0 0
Common stock issuances     1 2
Conversions of Class A to Class B common stock     (6) (10)
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 208 218 208 218
Balance at beginning of period     2 3
Common stock issuances     0 0
Common stock purchases     0 (1)
Balance at end of period 2 2 2 2
Class B common stock
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     712 729
Common stock purchases     (11.0) (18.0)
Conversions of Class A to Class B common stock     (6) (10)
Stock Issued During Period, Value, Conversion of Convertible Securities     0 0
Balance at end of period 707 721 707 721
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     232 364
Common stock issuances     147 149
Option premiums received (paid)     102 (399)
Common stock purchases     (481) (114)
Balance at end of period 0 0 0 0
Retained Earnings
        
Stockholders Equity Note [Roll Forward]        
Balance at beginning of period     6,925 7,997
Net income     1,365 2,108
Dividends ($0.57 and $0.52 per share)     (1,253) (1,199)
Common stock purchases     (882) (1,721)
Balance at end of period $ 6,155 $ 7,185 $ 6,155 $ 7,185
Common stock, cash paid for dividends, per share     $ 1.34 $ 1.24