Summary of Significant Accounting Policies (Basic and Diluted EPS Calculation for Continuing Operations) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Income from continuing operations	$ 159	$ 279	$ 536	$ 696	$ 28	$ 397	$ 507	$ 578	$ 1,670	$ 1,510	$ 1,795
Less: Net income attributable to non-controlling interests									20	20	27
Net income attributable to the Company									$ 1,650	$ 1,490	$ 1,768
Basic weighted average common shares outstanding (in shares)									506	513	519
Dilutive effect of potentially issuable common shares (in shares)									5	6	5
Dilutive weighted average common shares outstanding (in shares)									511	519	524
Average stock price used to calculate common stock equivalents (in dollars per share)									$ 83.13	$ 77.30	$ 63.51