Retirement Plans (Schedule of Change in Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning projected benefit obligations	$ 588	$ 529
Service cost	42	33	$ 36
Interest cost	10	11	10
Foreign exchange impact	60	(18)
Employee contributions	6	6
Actuarial losses	19	40
Acquisition	0	7
Benefits paid	(17)	(20)
Ending projected benefit obligations	708	588	$ 529
Ending accumulated benefit obligations	$ 675	$ 560