Quarterly report pursuant to Section 13 or 15(d)

Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail)

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Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Defined Benefit Pension Plan | U.S. Pension Benefits        
Net Periodic Cost:        
Service cost $ 415 $ 389 $ 831 $ 779
Interest cost 450 462 899 924
Expected return on assets (800) (712) (1,601) (1,424)
Amortization of prior service cost 48 48 97 96
Net periodic benefit cost 113 187 226 375
Defined Benefit Pension Plan | International Pension Benefits        
Net Periodic Cost:        
Service cost 16 14 32 29
Interest cost 11 10 23 20
Expected return on assets (19) (16) (39) (32)
Amortization of prior service cost 0 0 0 0
Net periodic benefit cost 8 8 16 17
U.S. Postretirement Medical Benefits        
Net Periodic Cost:        
Service cost 7 7 14 14
Interest cost 26 28 52 56
Expected return on assets (2) (1) (4) (3)
Amortization of prior service cost 2 2 4 4
Net periodic benefit cost $ 33 $ 36 $ 66 $ 71