Employee Benefits - Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits
Net Periodic Benefit Cost
Net Periodic Other Benefit Costs	$ 369	$ 241	$ 856	$ 678
Pension Benefits | United States
Net Periodic Benefit Cost
Service cost	124	101	373	304
Interest cost	89	100	265	298
Expected return on plan assets	(163)	(141)	(488)	(423)
Amortization of prior service costs (credits)	0	0	1	1
Amortization of actuarial losses (gains)	96	60	288	179
Settlement losses	184	87	304	207
Net Periodic Other Benefit Costs	330	207	743	566
Pension Benefits | International
Net Periodic Benefit Cost
Service cost	33	34	97	105
Interest cost	44	49	131	153
Expected return on plan assets	(52)	(56)	(155)	(171)
Amortization of prior service costs (credits)	2	3	7	9
Amortization of actuarial losses (gains)	12	4	33	15
Settlement losses	0	0	0	1
Net Periodic Other Benefit Costs	39	34	113	112
Other Benefits
Net Periodic Benefit Cost
Service cost	9	9	28	27
Interest cost	18	24	53	72
Amortization of prior service costs (credits)	(7)	(7)	(21)	(21)
Amortization of actuarial losses (gains)	1	(1)	3	(2)
Net Periodic Other Benefit Costs	$ 21	$ 25	$ 63	$ 76