Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10	$ 8	$ 20	$ 17
Interest cost	18	23	37	46
Expected return on plan assets	(47)	(44)	(95)	(89)
Amortization of net losses	13	11	26	22
Amortization of prior service benefit	0	0	0	0
Net benefit	(6)	(2)	(12)	(4)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	1	3	3
Interest cost	3	5	6	9
Expected return on plan assets	(3)	(3)	(6)	(7)
Amortization of net losses	0	0	0	0
Amortization of prior service benefit	(7)	(6)	(13)	(12)
Net benefit	$ (5)	$ (3)	$ (10)	$ (7)