Pension and Postretirement Benefit Plans - Components of net periodic benefit cost and other information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Non-operating expense
Total net periodic benefit cost (benefit)	$ (67)	$ (79)
Postretirement Benefits
Operating expense
Service cost	11	12
Non-operating expense
Interest cost	13	11
Expected return on plan assets	(18)	(19)
Amortization of transition asset	0	0
Amortization of prior service benefit	(7)	(8)
Amortization of net actuarial loss	10	14
Settlements, curtailments, special termination benefits and other	1	1
Total non-operating expense (benefit)	(1)	(1)
Total net periodic benefit cost (benefit)	10	11
UNITED STATES | Qualified and Non-qualified Pension Benefits
Operating expense
Service cost	64	72
Non-operating expense
Interest cost	104	90
Expected return on plan assets	(241)	(264)
Amortization of transition asset	0	0
Amortization of prior service benefit	(6)	(6)
Amortization of net actuarial loss	106	132
Settlements, curtailments, special termination benefits and other	0	0
Total non-operating expense (benefit)	(37)	(48)
Total net periodic benefit cost (benefit)	27	24
International | Qualified and Non-qualified Pension Benefits
Operating expense
Service cost	35	42
Non-operating expense
Interest cost	32	25
Expected return on plan assets	(72)	(81)
Amortization of transition asset	0	0
Amortization of prior service benefit	0	(1)
Amortization of net actuarial loss	11	27
Settlements, curtailments, special termination benefits and other	0	0
Total non-operating expense (benefit)	(29)	(30)
Total net periodic benefit cost (benefit)	$ 6	$ 12