Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ (3)	$ (2)	$ (11)	$ (6)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	2	7	7
Interest cost	6	6	19	18
Amortization of actuarial losses	2	5	6	14
Amortization of prior service credit	14	15	43	45
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	8	17	24
Interest cost	26	23	79	71
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	35	37	105	113
Amortization of actuarial losses	16	16	47	48
Net periodic benefit cost	$ 13	$ 10	$ 38	$ 30