Acquisitions / Dispositions (Pro-Forma Information) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combinations [Abstract]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		$ 25	$ 124
Revenue	$ 14,100	13,724	13,528
Income from continuing operations	1,514	1,787	1,643
Net income attributable to the Company	$ 1,496	$ 1,759	$ 1,606
Basic net income per share:
Basic net income per share - Continuing operations (in dollars per share)	$ 2.91	$ 3.39	$ 3.02
Basic net income per share - Net income attributable to the Company (in dollars per share)	2.92	3.39	3.02
Diluted net income per share:
Diluted net income per share - Continuing operations (in dollars per share)	2.88	3.36	2.99
Diluted net income per share - Net income attributable to the Company (in dollars per share)	$ 2.88	$ 3.36	$ 2.99
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual		$ 4	$ 7
Business Combination, Acquisition Related Costs	$ 3	$ 14

Business Acquisition, Pro Forma Earnings Per Share, Basic [Abstract]

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Business Acquisition, Pro Forma Earnings Per Share, Diluted [Abstract]

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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Per basic share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period.

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Per diluted share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period.

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Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

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This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
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This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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