Fair Value (Schedule of Fair Value Measurements, Liabilities, Using Significant Unobservable Inputs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, beginning balance, Liabilities	$ 162	$ 155	$ 115	$ 201
Transfers into Level 3, Liabilities	0	0	0	0
Transfers out of Level 3, Liabilities	0	0	0	0
Recorded in Revenue, Liabilities	24	(78)	74	(125)
Recorded in Other Comprehensive Income, Liabilities	0	0	0	0
Purchases, Liabilities	0	0	0	0
Issuances, Liabilities	10	150	35	195
Sales, Liabilities	0	0	0	0
Settlements, Liabilities	(79)	(61)	(107)	(105)
Fair Value, ending balance, Liabilities	117	166	117	166
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 2012	29	(52)	42	(68)
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		20
Recorded in Revenue, Liabilities	0	0		0
Issuances, Liabilities	0	0		0
Settlements, Liabilities	0	(20)		(20)
Fair Value, ending balance, Liabilities	0	0	0	0
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 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	162	135	115	181
Recorded in Revenue, Liabilities	24	(78)	74	(125)
Issuances, Liabilities	10	150	35	195
Settlements, Liabilities	(79)	(41)	(107)	(85)
Fair Value, ending balance, Liabilities	117	166	117	166
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 2012	29	(52)	42	(68)
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	153	126	106	161
Recorded in Revenue, Liabilities	24	(78)	74	(115)
Issuances, Liabilities	10	150	35	195
Settlements, Liabilities	(79)	(41)	(107)	(84)
Fair Value, ending balance, Liabilities	108	157	108	157
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 2012	29	(52)	42	(68)
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				(10)
Issuances, Liabilities				0
Settlements, Liabilities				(1)
Fair Value, ending balance, Liabilities		0		0
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 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	9	9
Recorded in Revenue, Liabilities	0	0	0	0
Issuances, Liabilities	0		0	0
Settlements, Liabilities	0	0	0	0
Fair Value, ending balance, Liabilities	9	9	9	9
Change in Unrealized (Gains) Losses Related to Financial Instruments Held as of June 30, 2012		$ 0	$ 0	$ 0