Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment	$ 0	$ 0	$ 1	$ 0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	3	7	7
Interest cost	5	6	15	19
Amortization of actuarial losses	4	2	12	6
Amortization of prior service credit	14	14	44	43
Net periodic benefit cost	(3)	(3)	(10)	(11)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	6	18	17
Interest cost	22	26	65	79
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	36	35	108	105
Amortization of actuarial losses	17	16	53	47
Net periodic benefit cost	$ 9	$ 13	$ 29	$ 38