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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

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