Pensions and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10	$ 9	$ 30	$ 26
Interest cost	19	24	56	70
Expected return on plan assets	(48)	(45)	(143)	(134)
Amortization of net losses	13	11	39	33
Amortization of prior service benefit	0	0	0	0
Net benefit	(6)	(1)	(18)	(5)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2	5	5
Interest cost	3	4	9	13
Expected return on plan assets	(4)	(4)	(10)	(11)
Amortization of net losses	0	0	0	0
Amortization of prior service benefit	(6)	(6)	(19)	(18)
Net benefit	$ (5)	$ (4)	$ (15)	$ (11)