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
Mar. 31, 2018
Mar. 31, 2017
Defined Benefit Pension Plan | U.S. Pension Benefits    
Net Periodic Cost:    
Service cost $ 416 $ 390
Interest cost 449 462
Expected return on assets (801) (712)
Amortization of:    
Amortization of prior service cost 49 48
Net periodic benefit cost 113 188
Defined Benefit Pension Plan | International Pension Benefits    
Net Periodic Cost:    
Service cost 16 15
Interest cost 12 10
Expected return on assets (20) (16)
Amortization of:    
Amortization of prior service cost 0 0
Net periodic benefit cost 8 9
U.S. Postretirement Medical Benefits    
Net Periodic Cost:    
Service cost 7 7
Interest cost 26 28
Expected return on assets (2) (2)
Amortization of:    
Amortization of prior service cost 2 2
Net periodic benefit cost $ 33 $ 35