Accumulated Other Comprehensive Income (Loss) - Income (Expense) Effect of Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Affected Line Item on the Statements of Income [Line Items]
Other Income (Expense) - net	$ 106	$ (35)	$ 297	$ (112)
Interest Expense	(244)	(230)	(718)	(669)
Income Taxes	(103)	(116)	(362)	(321)
Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total After-tax	(20)	(34)	(84)	(123)
Qualifying Derivatives [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total Pre-tax	17	1	25	(30)
Income Taxes	(3)	(1)	(4)	6
Total After-tax	14	0	21	(24)
Qualifying Derivatives [Member] | Interest Rate Swaps [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Interest Expense	(2)	(2)	(6)	(7)
Qualifying Derivatives [Member] | Cross Currency Swaps [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Other Income (Expense) - net	18	2	30	(24)
Interest Expense	1	1	1	1
Equity Investees Accumulated Other Comprehensive Income [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Other Income (Expense) - net	0	0	0	(1)
Total Pre-tax	0	0	0	(1)
Income Taxes	0	0	0	0
Total After-tax	0	0	0	(1)
Defined Benefit Plans [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total Pre-tax	(43)	(45)	(132)	(127)
Income Taxes	9	11	27	29
Total After-tax	(34)	(34)	(105)	(98)
Defined Benefit Plans [Member] | Prior Service Costs [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total Pre-tax	(1)	(1)	(2)	(2)
Defined Benefit Plans [Member] | Net Actuarial Loss [Member] | Amounts Reclassified From Accumulated Other Comprehensive Income [Member]
Affected Line Item on the Statements of Income [Line Items]
Total Pre-tax	$ (42)	$ (44)	$ (130)	$ (125)