Goodwill and Intangible Assets Weighted-average useful lives assigned to finite-lived intangible assets acquired in business combinations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 773	$ 889
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	11 years	16 years
Customer-Related Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 324	$ 785
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	13 years	17 years
Trademarks and Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 367	$ 82
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	11 years	4 years
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	$ 82	$ 22
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years	5 years