Employee Benefits - Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Benefits
Net Periodic Benefit Cost
Net Periodic Other Benefit Costs	$ 297	$ 245	$ 775	$ 487
Pension Benefits | United States
Net Periodic Benefit Cost
Service cost	108	125	225	249
Interest cost	64	88	119	176
Expected return on plan assets	(145)	(163)	(294)	(325)
Amortization of prior service costs (credits)	0	0	1	1
Amortization of actuarial losses (gains)	73	96	177	192
Settlement losses	151	60	468	120
Net Periodic Other Benefit Costs	251	206	696	413
Pension Benefits | International
Net Periodic Benefit Cost
Service cost	37	32	71	64
Interest cost	36	44	69	87
Expected return on plan assets	(43)	(51)	(89)	(103)
Amortization of prior service costs (credits)	2	3	4	5
Amortization of actuarial losses (gains)	14	11	24	21
Settlement losses	0	0	0	0
Net Periodic Other Benefit Costs	46	39	79	74
Other Benefits
Net Periodic Benefit Cost
Service cost	10	10	21	19
Interest cost	13	17	26	35
Amortization of prior service costs (credits)	(6)	(8)	(13)	(14)
Amortization of actuarial losses (gains)	4	2	8	2
Net Periodic Other Benefit Costs	$ 21	$ 21	$ 42	$ 42