Fair Value (Schedule of Fair Value Measurements, Liabilities, Using Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	$ 115	$ 201
Transfers into Level 3, Liabilities	0	0
Transfers out of Level 3, Liabilities	0	0
Recorded in Revenue, Liabilities	61	(84)
Recorded in Other Comprehensive Income, Liabilities	0	0
Purchases, Liabilities	0	0
Issuances, Liabilities	50	111
Sales, Liabilities	0	0
Settlements, Liabilities	(64)	(73)
Fair Value, ending balance, Liabilities	162	155
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012	39	(51)
Accrued expenses and other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	0	20
Recorded in Revenue, Liabilities	0	0
Purchases, Liabilities
Issuances, Liabilities	0	0
Settlements, Liabilities	0	0
Fair Value, ending balance, Liabilities	0	20
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012	0
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	115	181
Recorded in Revenue, Liabilities	61	(84)
Purchases, Liabilities
Issuances, Liabilities	50	111
Settlements, Liabilities	(64)	(73)
Fair Value, ending balance, Liabilities	162	135
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012	39	(51)
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	106	161
Recorded in Revenue, Liabilities	61	(75)
Issuances, Liabilities	50	111
Settlements, Liabilities	(64)	(71)
Fair Value, ending balance, Liabilities	153	126
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012	39	(51)
Interest-rate contracts | Accrued expenses and other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities		11
Recorded in Revenue, Liabilities		(9)
Issuances, Liabilities		0
Settlements, Liabilities		(2)
Fair Value, ending balance, Liabilities		0
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012		0
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
Settlements, Liabilities	0	0
Fair Value, ending balance, Liabilities	9	9
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of March 31, 2012	$ 0	$ 0