Derivatives and Hedging - Offsetting of financial liabilities and derivative liabilities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	$ 58		$ 93
Gross Amounts Offset in the Statement of Financial Position	(14)		(30)
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	44	[1]	63	[1]
Other Current Liabilities [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	52		51
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	40		23
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	6		42
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	4		40
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	58	[2]	93	[2]
Gross Amounts Offset in the Statement of Financial Position	(14)		(30)
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	44	[1]	63	[1]
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	0	[2]	0	[2]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	0	[1]	0	[1]
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	58	[2]	93	[2]
Gross Amounts Offset in the Statement of Financial Position	(14)		(30)
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	44	[1]	63	[1]
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	58	[2]	93	[2]
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Gross Amounts of Recognized Liabilities	0	[2],[3]	0	[2],[3]
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Liabilities Presented in the Statement of Financial Position (2)	$ 0	[1]	$ 0	[1]

[1] Included within Other current liabilities ($40 million in 2014 and $23 million in 2013, respectively) or Other non-current liabilities ($4 million in 2014 and $40 million in 2013, respectively)

[2] Included within Other current liabilities ($52 million in 2014 and $51 million in 2013, respectively) or Other non-current liabilities ($6 million in 2014 and $42 million in 2013, respectively)

[3] These contracts typically are for 30 day durations and executed close to the last day of the most recent reporting month, thereby resulting in nominal fair values at the balance sheet date.