Derivative Instruments - Location and Amount of Gains (Losses) Reported in Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative contracts
Approximate loss amount to be reclassified from accumulated other comprehensive income (loss), net of tax to income			$ (61)
Cash Flow Hedges \| Foreign exchange forward contracts
Derivative contracts
Gain (loss) recognized in other comprehensive income	$ (24)	$ (44)	(48)	$ 8
Gain (loss) reclassified from Accumulated other comprehensive income into income (effective portion)	(12)	4	(25)	31
Cash Flow Hedges \| Diesel forward contracts
Derivative contracts
Gain (loss) recognized in other comprehensive income	(12)	(9)	(13)	(8)
Gain (loss) reclassified from Accumulated other comprehensive income into income (effective portion)	(7)	(1)	(20)
Cash Flow Hedges \| Interest rate contracts
Derivative contracts
Gain (loss) reclassified from Accumulated other comprehensive income into income (effective portion)	(5)	$ (5)	(14)	$ (14)
Other income, net \| Cash Flow Hedges \| Diesel forward contracts
Derivative contracts
Gain (loss) reclassified from Accumulated other comprehensive income into income (ineffective portion)	$ 1		$ 2

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1),(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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