Fair Value - Schedule of Fair Value Measurements, Liabilities, Using Significant Unobservable Inputs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	$ 83	$ 26
Recorded in Revenue, Liabilities	109	(10)
Issuances, Liabilities	(37)	(7)
Settlements, Liabilities	(48)	(6)
Fair Value, ending balance, Liabilities	181	17
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of end of period	93	(5)
Derivative instruments, liabilities \| Accrued expenses and other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	83	26
Recorded in Revenue, Liabilities	109	(10)
Issuances, Liabilities	(37)	(7)
Settlements, Liabilities	(48)	(6)
Fair Value, ending balance, Liabilities	181	17
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of end of period	93	(5)
Foreign exchange contracts \| Accrued expenses and other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	74	17
Recorded in Revenue, Liabilities	109	(10)
Issuances, Liabilities	(37)	(7)
Settlements, Liabilities	(48)	(6)
Fair Value, ending balance, Liabilities	172	8
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of end of period	93	(5)
Other \| Accrued expenses and other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	9	9
Recorded in Revenue, Liabilities	0	0
Issuances, Liabilities	0	0
Settlements, Liabilities	0	0
Fair Value, ending balance, Liabilities	9	9
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of end of period		$ 0

Change in Unrealized Gains (Losses) Related to Financial Instruments, Liabilities, Held at Period End

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- Definition

Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

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