Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill	$ 2,374	$ 2,246
Finite-Lived Intangible Assets, Period Increase (Decrease)	81
Intangible Assets Foreign Currency Translation Gain (Loss)	79
Goodwill, Foreign Currency Translation Gain (Loss)	98
Amortization of Intangible Assets	122	113	$ 75
Amortization expense of intangible assets next 12 months	109
Finite-Lived Intangible Assets, Amortization Expense, Year Two	107
Finite-Lived Intangible Assets, Amortization Expense, Year Three	105
Finite-Lived Intangible Assets, Amortization Expense, Year Four	100
Finite-Lived Intangible Assets, Amortization Expense, Year Five	95
Series of Individually Immaterial Business Acquisitions [Member]
Goodwill
Goodwill	$ 33	$ 72