Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2
Interest cost	5	6
Amortization of actuarial losses	4	2
Amortization of prior service credit	15	14
Net periodic benefit cost	(4)	(4)
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	6
Interest cost	22	26
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	36	35
Amortization of actuarial losses	18	15
Net periodic benefit cost	$ 10	$ 12