Fair Value Measurements (Non-Recurring Measurement) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	$ 2,418	$ 2,412
Fair Value, Inputs, Level 3 [Member] | Financing receivables and loans held for sale [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	2,693	4,094
Fair Value, Inputs, Level 3 [Member] | Cost and equity method investments [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	923	313
Fair Value, Inputs, Level 3 [Member] | Long Lived Assets, Including Real Estate [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	2,125	2,182
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	1,249	1,652
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation		11.10%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	1.50%	1.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	38.00%	29.90%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation	14.60%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	5,888	4,977
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation		3.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	1.50%	2.10%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	10.50%	13.10%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation	4.10%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	747	865
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation		13.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	0.80%	1.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	30.60%	25.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation	14.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	444	360
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	4.70%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	5.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation	5.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Weighted Average Cost Of Capital [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Cost Of Capital Used For Level Three Valuation		8.70%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Weighted Average Cost Of Capital [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Cost Of Capital Used For Level Three Valuation	8.90%	8.70%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Weighted Average Cost Of Capital [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Cost Of Capital Used For Level Three Valuation	9.20%	10.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach Valuation Techniques [Member] | Weighted Average Cost Of Capital [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Cost Of Capital Used For Level Three Valuation	9.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	1,915	2,835
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation		8.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	5.50%	3.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	16.70%	14.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation	8.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | EBITDA Multiple [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple Used For Level Three Valuation	4.3	2.0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | EBITDA Multiple [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple Used For Level Three Valuation	7.0	6.0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise Valuation Techniques [Member] | EBITDA Multiple [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple Used For Level Three Valuation	5.8	4.8
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	387	72
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	11.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	11.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount Rate [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate Used For Level Three Valuation	11.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation		12.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	8.50%	9.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	10.60%	12.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation	10.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount For Lack Of Marketability [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate For Lack Of Marketability Used For Level Three Valuation	5.70%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount For Lack Of Marketability [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate For Lack Of Marketability Used For Level Three Valuation	5.90%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach Valuation Techniques [Member] | Discount For Lack Of Marketability [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Discount Rate For Lack Of Marketability Used For Level Three Valuation	5.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	$ 622	$ 985
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation		7.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	5.40%	4.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation	14.50%	14.60%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member] | Capitalization Rate Unobservable Inputs [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted Average Capitalization Rate Used For Level Three Valuation	8.30%