Fair Value Measurements (Non-Recurring) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	$ 2,412
Financing receivables and loans held for sale [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustments To Assets Measured At Fair Value On Non Recurring Basis	(595)	(857)
Cost and equity method investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustments To Assets Measured At Fair Value On Non Recurring Basis	(153)	(272)
Long Lived Assets, Including Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustments To Assets Measured At Fair Value On Non Recurring Basis	(624)	(1,410)
Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustments To Assets Measured At Fair Value On Non Recurring Basis	(1,372)	(2,539)
Fair Value, Inputs, Level 2 [Member] | Financing receivables and loans held for sale [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	366	158
Fair Value, Inputs, Level 2 [Member] | Cost and equity method investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	8	0
Fair Value, Inputs, Level 2 [Member] | Long Lived Assets, Including Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	702	1,343
Fair Value, Inputs, Level 2 [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	1,076	1,501
Fair Value, Inputs, Level 3 [Member] | Financing receivables and loans held for sale [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	4,094	5,159
Fair Value, Inputs, Level 3 [Member] | Cost and equity method investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	313	402
Fair Value, Inputs, Level 3 [Member] | Long Lived Assets, Including Real Estate [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	2,184	3,254
Fair Value, Inputs, Level 3 [Member] | Total [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value assets measured on non recurring basis	$ 6,591	$ 8,815