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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 158 $ 149 $ 133  
Share-based compensation, net of tax 103 97 86  
Unrecognized compensation cost $ 91      
Period over which unrecognized compensation costs are expected to be recognized (years) 1 year 8 months 18 days      
Cash received from exercise of stock options $ 71 106 174  
Realized tax benefits from stock-based compensation activities $ 203 $ 219 $ 213  
Weighted average remaining contractual life, vested 3 years      
Number of years over which equity awards expire 10 years      
Number of shares authorized (in shares) 10,000      
Shares reserved for issuance (in shares) 6,000      
Number of years over which equity awards vest 3 years      
Number of stock options, outstanding (in shares) 2,200 3,000    
Weighted average exercise price, outstanding (in dollars per share) $ 82.71 $ 85.82    
Weighted average remaining contractual life, outstanding 2 years 6 months      
Aggregate intrinsic value, outstanding $ 533      
Number of stock options, vested (in shares) 800      
Weighted average exercise price, vested (in dollars per share) $ 95.06      
Risk-free interest rate       0.78%
Dividend yield       5.40%
Volatility factors       28.00%
Expected option life (in years)       5 years
Restricted Stock Units (RSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of stock, granted, in shares 519 679 595  
Average grant date fair value per unit (in dollars per share) $ 254.58 $ 206.69 $ 192.47  
Number of years over which equity awards vest 3 years      
Performance Stock Units (PSUs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Number of stock, granted, in shares 100      
Number of years over which equity awards vest 3 years      
Performance Stock Units (PSUs) | Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of shares that can be earned from stock awards, as a percentage of the target award 0.00%      
Performance Stock Units (PSUs) | Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Range of shares that can be earned from stock awards, as a percentage of the target award 200.00%      
Performance Stock Units (PSUs) | Half Of PSUs Granted In Period        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Average grant date fair value per unit (in dollars per share) $ 254.53      
Performance Stock Units (PSUs) | Remaining Half Of PSUs Granted In Period        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Average grant date fair value per unit (in dollars per share) $ 266.44