Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	$ 1	$ 0	$ 1	$ 0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	2	5	4
Interest cost	5	7	10	13
Amortization of actuarial losses	4	2	8	4
Amortization of prior service credit	15	15	30	29
Net periodic benefit cost	(3)	(4)	(7)	(8)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5	12	11
Interest cost	21	27	43	53
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	36	35	72	70
Amortization of actuarial losses	18	16	36	31
Net periodic benefit cost	$ 10	$ 13	$ 20	$ 25