Benefit Plans - Changes in benefit obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in benefit obligation
Service cost	$ 104	$ 108	$ 125
Interest cost	199	221	254
Pension benefits
Change in benefit obligation
Benefit obligation, beginning of year	7,763	7,139
Service cost	103	104	117
Interest cost	191	210	240
Participant contributions	0	0
Remeasurement of projected benefit obligation (gains) losses	(309)	813
Benefits paid	(1,242)	(522)
Plan amendments	0	0
Translation adjustment and other	(6)	(1)
Curtailment losses (gains)	0	20
Benefit obligation, end of year	6,500	7,763	7,139
Change in plan assets
Fair value of plan assets, beginning of year	6,987	6,192
Actual return on plan assets	764	1,300
Employer contribution	22	18
Benefits paid	(1,242)	(522)
Translation adjustment and other	(6)	(1)
Fair value of plan assets, end of year	6,525	6,987	6,192
Funded status	25	(776)
Prior service credit	(28)
Unamortized pension and other postretirement prior service credit	(28)	(78)
Postretirement benefits
Change in benefit obligation
Benefit obligation, beginning of year	318	397
Service cost	1	4	8
Interest cost	8	11	14
Participant contributions	16	14
Remeasurement of projected benefit obligation (gains) losses	(16)	22
Benefits paid	(43)	(37)
Plan amendments	0	(102)
Translation adjustment and other	0	(1)
Curtailment losses (gains)	0	10
Benefit obligation, end of year	284	318	$ 397
Change in plan assets
Fair value of plan assets, beginning of year
Employer contribution	27	23
Fair value of plan assets, end of year
Funded status	(284)	(318)
Prior service credit	(65)
Unamortized pension and other postretirement prior service credit	$ (65)	$ (89)