Quarterly report pursuant to Section 13 or 15(d)

Activity in Accumulated Other Comprehensive Income (Loss) (Phantoms) (Detail)

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Activity in Accumulated Other Comprehensive Income (Loss) (Phantoms) (Detail) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Balance at beginning of period     $ (4,867)      
Change in foreign currency translation adjustment, net of tax $ (28) $ 32 (112) $ 86    
Balance at end of period (5,288) (4,224) (5,288) (4,224)    
Foreign currency translation gain (loss):            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Balance at beginning of period     (930) (1,016)    
Change in foreign currency translation adjustment, net of tax     (112) 86    
Reclassification to retained earnings pursuant to the early adoption of ASU 2018-02         $ (47) $ 0
Balance at end of period (1,089) (930) (1,089) (930)    
Aggregate adjustment for the period, tax     26 (146)    
Unrealized gain (loss) on marketable securities, net of tax:            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Balance at beginning of period     (2) (1)    
Balance at end of period (6) 0 (6) 0    
Current period changes in fair value, tax effect     (2) 1    
Reclassification to earnings, tax effect     1 0    
Unrealized gain (loss) on cash flow hedges, net of tax:            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Balance at beginning of period     (366) (45)    
Reclassification to retained earnings pursuant to the early adoption of ASU 2018-02         (79) 0
Balance at end of period (130) (323) (130) (323)    
Current period changes in fair value, tax effect     81 (162)    
Reclassification to earnings, tax effect     19 (6)    
Accumulated Defined Benefit Plans Adjustment [Member]            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Balance at beginning of period     (3,569) (3,421)    
Reclassification to retained earnings pursuant to the early adoption of ASU 2018-02         $ (609) $ 0
Balance at end of period $ (4,063) $ (2,971) (4,063) (2,971)    
Reclassification to earnings, tax effect     36 56    
Other Comprehensive Income (Loss), Defined Benefit Plan, Adjustment for Settlement or Curtailment Gain (Loss), Tax     $ 0 $ 214