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 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Defined Benefit Pension Plan | U.S. Pension Benefits        
Net Periodic Cost:        
Service cost $ 415 $ 382 $ 1,246 $ 1,161
Interest cost 450 445 1,349 1,369
Expected return on assets (800) (730) (2,401) (2,154)
Amortization of prior service cost 48 48 145 144
Net periodic benefit cost 113 145 339 520
Defined Benefit Pension Plan | International Pension Benefits        
Net Periodic Cost:        
Service cost 15 15 47 44
Interest cost 11 10 34 30
Expected return on assets (19) (17) (58) (49)
Amortization of prior service cost 0 1 0 1
Net periodic benefit cost 7 9 23 26
U.S. Postretirement Medical Benefits        
Net Periodic Cost:        
Service cost 7 7 21 21
Interest cost 26 28 78 84
Expected return on assets (2) (2) (6) (5)
Amortization of prior service cost 2 1 6 5
Net periodic benefit cost $ 33 $ 34 $ 99 $ 105