Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Allowance for doubtful accounts receivable, current	$ (12)	$ (22)
Stockholders’ equity:
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	10,000,000us-gaap_PreferredStockSharesAuthorized	10,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued (in shares)	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	2,400,000,000us-gaap_CommonStockSharesAuthorized	2,400,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued (in shares)	1,740,815,939us-gaap_CommonStockSharesIssued	1,740,815,939us-gaap_CommonStockSharesIssued
Treasury stock (in shares)	694,189,127us-gaap_TreasuryStockShares	658,012,970us-gaap_TreasuryStockShares

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.

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