Retirement Benefits (Schedule of Total Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total recognized in net periodic benefit cost and other comprehensive loss (income)	$ 63	$ (10)	$ 31
United States | Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recognized in net periodic benefit cost and other comprehensive loss (income)	0	5	2
Foreign Plan | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Total recognized in net periodic benefit cost and other comprehensive loss (income)	(147)	(513)	21
Foreign Plan | Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recognized in net periodic benefit cost and other comprehensive loss (income)	$ (5)	$ (14)	$ 10