Business Segment Information Business Segment Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended	48 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2022
Segment Reporting Information [Line Items]
Asset Write-Offs, Impairments, And Related Charges	$ 155	$ 16	$ 297	$ 422
Restructuring Charges	43	23	103	89
Employee Retention and Severances Expenses and Other Benefits-Related Costs [Member]
Segment Reporting Information [Line Items]
Restructuring Charges	$ 43	$ 23	$ 103	$ 89
Employee Retention and Severances Expenses and Other Benefits-Related Costs [Member] | Subsequent Event [Member]
Segment Reporting Information [Line Items]
Restructuring Charges					$ 155	$ 215