Fair Value Measurements (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2012 Securitizations credit_rating	Dec. 31, 2012	Dec. 31, 2011
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
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		$ 1,256,000,000	$ 1,365,000,000
Fair Value of Derivative Liabilities		400,000,000	286,000,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		324,000,000	241,000,000
Marketable securities		2,106,000,000	3,835,000,000
Fair Value of Derivative Assets		1,256,000,000	1,365,000,000
Total assets at fair value		3,686,000,000	5,441,000,000
Fair Value of Derivative Liabilities		400,000,000	286,000,000
Total liabilities at fair value		400,000,000	286,000,000
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		6,300,000,000	5,700,000,000
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		2,600,000,000	2,800,000,000
Fair Value, Measurements, Recurring [Member] | U.S. Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		200,000,000	1,000,000
Marketable securities		620,000,000	619,000,000
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		20,000,000	75,000,000
Marketable securities		12,000,000	713,000,000
Fair Value, Measurements, Recurring [Member] | Non-U.S. government agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	150,000,000
Marketable securities		95,000,000	778,000,000
Fair Value, Measurements, Recurring [Member] | Corporate debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		1,000,000	0
Marketable securities		1,155,000,000	1,186,000,000
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		67,000,000	88,000,000
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		103,000,000	15,000,000
Marketable securities		142,000,000	444,000,000
Fair Value, Measurements, Recurring [Member] | Other liquid investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Marketable securities		15,000,000	7,000,000
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		1,247,000,000	1,163,000,000
Fair Value of Derivative Liabilities		256,000,000	237,000,000
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		9,000,000	53,000,000
Fair Value of Derivative Liabilities		27,000,000	37,000,000
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		0	12,000,000
Fair Value of Derivative Liabilities		117,000,000	12,000,000
Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		0	137,000,000
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		200,000,000	1,000,000
Marketable securities		620,000,000	619,000,000
Fair Value of Derivative Assets		0	0
Total assets at fair value		820,000,000	620,000,000
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		200,000,000	1,000,000
Marketable securities		620,000,000	619,000,000
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]
Cash equivalents - financial instruments		0	0
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 1 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		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		124,000,000	240,000,000
Marketable securities		1,486,000,000	3,216,000,000
Fair Value of Derivative Assets		1,256,000,000	1,228,000,000
Total assets at fair value		2,866,000,000	4,684,000,000
Fair Value of Derivative Liabilities		400,000,000	286,000,000
Total liabilities at fair value		400,000,000	286,000,000
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		20,000,000	75,000,000
Marketable securities		12,000,000	713,000,000
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]
Cash equivalents - financial instruments		0	150,000,000
Marketable securities		95,000,000	778,000,000
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		1,000,000	0
Marketable securities		1,155,000,000	1,186,000,000
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		67,000,000	88,000,000
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		103,000,000	15,000,000
Marketable securities		142,000,000	444,000,000
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		15,000,000	7,000,000
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		1,247,000,000	1,163,000,000
Fair Value of Derivative Liabilities		256,000,000	237,000,000
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		9,000,000	53,000,000
Fair Value of Derivative Liabilities		27,000,000	37,000,000
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		0	12,000,000
Fair Value of Derivative Liabilities		117,000,000	12,000,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents - financial instruments		0	0
Marketable securities		0	0
Fair Value of Derivative Assets		0	137,000,000
Total assets at fair value		0	137,000,000
Fair Value of Derivative Liabilities		0	0
Total liabilities at fair value		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [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 3 [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 3 [Member] | Non-U.S. government agencies [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 3 [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 3 [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 3 [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 3 [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 3 [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 3 [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 3 [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 3 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair Value of Derivative Assets		$ 0	$ 137,000,000