Pensions and Other Postretirement Benefits (Net Periodic Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ (4)	$ (2)	$ (8)	$ (4)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	3	4	5
Interest cost	7	6	13	12
Amortization of actuarial losses	2	4	4	9
Amortization of prior service credit	15	15	29	30
Pension
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	8	11	16
Interest cost	27	24	53	48
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	35	38	70	76
Amortization of actuarial losses	16	16	31	32
Net periodic benefit cost	$ 13	$ 10	$ 25	$ 20