Derivatives and Hedging (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivatives, Fair Value
Notional Amount	$ 1,673		$ 1,849
Derivative Assets	68		210
Gross Amounts Offset in the Statement of Financial Position	(33)		(160)
Net Amounts of Assets Presented in the Statement of Financial Position	35	[1]	50	[1]
Derivative Liabilities	132		251
Gross Amounts Offset in the Statement of Financial Position	33		160
Net Amounts of Liabilities Presented in the Statement of Financial Position	(99)	[2]	(91)	[2]
Derivatives accounted for as hedges:
Derivatives, Fair Value
Notional Amount	1,420		1,544
Derivative Assets	66		208
Gross Amounts Offset in the Statement of Financial Position	(32)		(160)
Net Amounts of Assets Presented in the Statement of Financial Position	34	[1]	48	[1]
Derivative Liabilities	131		250
Gross Amounts Offset in the Statement of Financial Position	32		160
Net Amounts of Liabilities Presented in the Statement of Financial Position	(99)	[2]	(90)	[2]
Interest rate contracts | Derivatives accounted for as hedges:
Derivatives, Fair Value
Notional Amount	322		336
Derivative Assets	16		17
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Assets Presented in the Statement of Financial Position	16	[1]	17	[1]
Derivative Liabilities	0		0
Gross Amounts Offset in the Statement of Financial Position	0		0
Net Amounts of Liabilities Presented in the Statement of Financial Position	0	[2]	0	[2]
Foreign exchange contracts | Derivatives accounted for as hedges:
Derivatives, Fair Value
Notional Amount	1,098		1,208
Derivative Assets	50		191
Gross Amounts Offset in the Statement of Financial Position	(32)		(160)
Net Amounts of Assets Presented in the Statement of Financial Position	18	[1]	31	[1]
Derivative Liabilities	131		250
Gross Amounts Offset in the Statement of Financial Position	32		160
Net Amounts of Liabilities Presented in the Statement of Financial Position	(99)	[2]	(90)	[2]
Foreign exchange contracts | Derivatives not accounted for as hedges:
Derivatives, Fair Value
Notional Amount	253		305
Derivative Assets	2		2
Gross Amounts Offset in the Statement of Financial Position	(1)		0
Net Amounts of Assets Presented in the Statement of Financial Position	1	[1]	2	[1]
Derivative Liabilities	1		1
Gross Amounts Offset in the Statement of Financial Position	1		0
Net Amounts of Liabilities Presented in the Statement of Financial Position	$ 0	[2]	$ (1)	[2]

[1] Included within Other current assets or Other non-current assets

[2] Included within Other current liabilities or Other non-current liabilities