Pension and Postretirement Benefit Plans - Components of net periodic benefit cost and other information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net periodic benefit cost (benefit)
Net periodic benefit cost (benefit)	$ (17)	$ (36)
Funded | Postretirement Benefits
Net periodic benefit cost (benefit)
Service cost	11	11
Interest cost	16	21
Expected return on plan assets	(20)	(20)
Amortization of prior service benefit	(8)	(7)
Amortization of net actuarial loss	12	9
Settlements, curtailments, special terminations and other	1
Total non-operating expense (benefit)	1	3
Net periodic benefit cost (benefit)	12	14
Funded | United States | Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	66	62
Interest cost	124	155
Expected return on plan assets	(255)	(260)
Amortization of prior service benefit	(6)	(6)
Amortization of net actuarial loss	134	91
Total non-operating expense (benefit)	(3)	(20)
Net periodic benefit cost (benefit)	63	42
Funded | International | Qualified and Non-qualified Pension Benefits
Net periodic benefit cost (benefit)
Service cost	38	33
Interest cost	31	39
Expected return on plan assets	(77)	(75)
Amortization of transition asset	1
Amortization of prior service benefit	(1)	(3)
Amortization of net actuarial loss	31	20
Total non-operating expense (benefit)	(15)	(19)
Net periodic benefit cost (benefit)	$ 23	$ 14