Postretirement Benefits (Estimated Total Future Postretirement Benefit Payments, Net Of Participant Contributions And Estimated Future Medicare Part D Subsidy Receipts) (Details) - Other Postretirement Benefits Plan [Member] $ in Millions	Dec. 31, 2017 USD ($)
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, year 1	$ 29
Benefit Payments, year 2	27
Benefit Payments, year 3	25
Benefit Payments, year 4	24
Benefit Payments, year 5	22
Benefit Payments, year 6-10	91
Subsidy Receipts, year 1	1
Subsidy Receipts, year 2	1
Subsidy Receipts, year 3	1
Subsidy Receipts, year 4	1
Subsidy Receipts, year 5	1
Subsidy Receipts, year 6-10	5
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Payments, year 1	1
Benefit Payments, year 2	1
Benefit Payments, year 3	1
Benefit Payments, year 4	0
Benefit Payments, year 5	0
Benefit Payments, year 6-10	$ 4