Net Periodic Benefit Cost for Pension and Postretirement Benefit Plans (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Pension Plan | U.S. Pension Benefits
Net Periodic Cost:
Service cost	$ 464	$ 359
Interest cost	494	517
Expected return on assets	(888)	(782)
Amortization of prior service cost	55	54
Net periodic benefit cost	125	148
Defined Benefit Pension Plan | International Pension Benefits
Net Periodic Cost:
Service cost	16	14
Interest cost	10	12
Expected return on assets	(21)	(19)
Amortization of prior service cost	0	0
Net periodic benefit cost	5	7
U.S. Postretirement Medical Benefits | U.S. Pension Benefits
Net Periodic Cost:
Service cost	7	6
Interest cost	23	27
Expected return on assets	(2)	(2)
Amortization of prior service cost	2	2
Net periodic benefit cost	$ 30	$ 33