Fair Value Measurements (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2012 Securitizations credit_rating	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Debt Security, Maturity Period for Classification as Cash Equivalent		90 days or less
Investment Security, Maturity Period for Classification as Marketable Security		greater than 90 days
Securities Purchased under Agreements to Resell Gross		$ 90,000,000	$ 25,000,000
Securitizations, Number of Transactions	2
Number of investment grade credit ratings, Number	2
Fair Value Measurement, Period After Which Fair Value of Collateral is Adjusted		greater than 120 days past due
Fair Value of Derivative Assets		784,000,000	1,256,000,000
Fair Value of Derivative Liabilities		380,000,000	400,000,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		247,000,000	324,000,000
Marketable securities		3,084,000,000	2,106,000,000
Fair Value of Derivative Assets		784,000,000	1,256,000,000
Total assets at fair value		4,115,000,000	3,686,000,000
Fair Value of Derivative Liabilities		380,000,000	400,000,000
Total liabilities at fair value		380,000,000	400,000,000
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Par value assets excluded from fair value by input		4,900,000,000	6,300,000,000
Fair Value, Measurements, Recurring [Member] | Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Par value assets excluded from fair value by input		2,300,000,000	2,600,000,000
Fair Value, Measurements, Recurring [Member] | U.S. Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		201,000,000	200,000,000
Marketable securities		1,235,000,000	620,000,000
Fair Value, Measurements, Recurring [Member] | U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	20,000,000
Marketable securities		400,000,000	12,000,000
Fair Value, Measurements, Recurring [Member] | Non-U.S. government agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		36,000,000	95,000,000
Fair Value, Measurements, Recurring [Member] | Corporate debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	1,000,000
Marketable securities		1,249,000,000	1,155,000,000
Fair Value, Measurements, Recurring [Member] | Mortgage-backed and other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		56,000,000	67,000,000
Fair Value, Measurements, Recurring [Member] | Non-U.S. government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		46,000,000	103,000,000
Marketable securities		108,000,000	142,000,000
Fair Value, Measurements, Recurring [Member] | Other liquid investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		0	15,000,000
Fair Value, Measurements, Recurring [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		744,000,000	1,247,000,000
Fair Value of Derivative Liabilities		316,000,000	256,000,000
Fair Value, Measurements, Recurring [Member] | Foreign currency exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		14,000,000	9,000,000
Fair Value of Derivative Liabilities		6,000,000	27,000,000
Fair Value, Measurements, Recurring [Member] | Cross-currency interest rate swap contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		26,000,000	0
Fair Value of Derivative Liabilities		58,000,000	117,000,000
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		201,000,000	200,000,000
Marketable securities		1,235,000,000	620,000,000
Fair Value of Derivative Assets		0	0
Total assets at fair value		1,436,000,000	820,000,000
Fair Value of Derivative Liabilities		0	0
Total liabilities at fair value		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		201,000,000	200,000,000
Marketable securities		1,235,000,000	620,000,000
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	0
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Non-U.S. government agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	0
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-backed and other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Non-U.S. government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	0
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other liquid investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		0	0
Fair Value of Derivative Liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign currency exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		0	0
Fair Value of Derivative Liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Cross-currency interest rate swap contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		0	0
Fair Value of Derivative Liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		46,000,000	124,000,000
Marketable securities		1,849,000,000	1,486,000,000
Fair Value of Derivative Assets		784,000,000	1,256,000,000
Total assets at fair value		2,679,000,000	2,866,000,000
Fair Value of Derivative Liabilities		380,000,000	400,000,000
Total liabilities at fair value		380,000,000	400,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	0
Marketable securities		0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	20,000,000
Marketable securities		400,000,000	12,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Non-U.S. government agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		36,000,000	95,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	1,000,000
Marketable securities		1,249,000,000	1,155,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-backed and other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		56,000,000	67,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Non-U.S. government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		46,000,000	103,000,000
Marketable securities		108,000,000	142,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other liquid investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		0	15,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest rate contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		744,000,000	1,247,000,000
Fair Value of Derivative Liabilities		316,000,000	256,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign currency exchange contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		14,000,000	9,000,000
Fair Value of Derivative Liabilities		6,000,000	27,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Cross-currency interest rate swap contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		26,000,000	0
Fair Value of Derivative Liabilities		$ 58,000,000	$ 117,000,000