Business Restructuring (Schedule of Restructuring Activity) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018 USD ($) employee position	Dec. 31, 2017 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Employees Impacted | employee	798	949
Number Of Employees Included In Plan Who Ceased Employment In Period | employee	(151)
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring Reserves, Deductions	$ (17)
Restructuring Reserve, Translation Adjustment	2
Restructuring Reserve	$ 87	$ 102
2016 Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, expected number of positions eliminated | position	2,000