Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Consolidated Balance Sheet
Allowances for doubtful accounts receivable	$ 88	$ 91
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued (in shares)	944,033,056	944,033,056
Treasury stock (in shares)	347,306,778	334,702,932
Common stock, Shares outstanding (in shares)	596,726,278	609,330,124

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
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Face amount or stated value per share of common stock.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
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Number of previously issued common shares repurchased by the issuing entity and held in treasury.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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