Acquisitions and Dispositions (Pro-Forma Information) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Combinations [Abstract]
Revenue	$ 3,514	$ 3,408	$ 11,350	$ 10,569
Net income attributable to the Company	$ 275	$ 392	$ 1,502	$ 1,465
Basic net income per share:
Basic net income per share attributable to the Company (in dollars per share)	$ 0.55	$ 0.77	$ 2.97	$ 2.85
Diluted net income per share:
Diluted net income per share attributable to the Company (in dollars per share)	$ 0.54	$ 0.76	$ 2.93	$ 2.82