Fair Value Measurements (Level 3 Measurements) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 2,947	$ 2,816
Individually Insignificant Recurring Fair Value Measurements	240	327
Individually Insignificant NonRecurring Fair Value Measurements	100	571
Level 3
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	1,325	1,460
Level 3 | Recurring | US Corporate | Income Approach
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	985	898
Level 3 | Recurring | US Corporate | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	1.50%	1.50%
Level 3 | Recurring | US Corporate | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	10.00%	13.30%
Level 3 | Recurring | US Corporate | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	6.20%	6.50%
Level 3 | Recurring | State And Municipal Debt | Income Approach
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	478
Level 3 | Recurring | State And Municipal Debt | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	2.00%
Level 3 | Recurring | State And Municipal Debt | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.20%
Level 3 | Recurring | State And Municipal Debt | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	3.30%
Level 3 | Recurring | Asset-backed | Income Approach
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	7,244	6,854
Level 3 | Recurring | Asset-backed | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	1.90%	1.20%
Level 3 | Recurring | Asset-backed | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	11.00%	10.50%
Level 3 | Recurring | Asset-backed | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.00%	3.70%
Level 3 | Recurring | Corporate - non-U.S. | Income Approach
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	633	819
Level 3 | Recurring | Corporate - non-U.S. | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	0.20%	1.40%
Level 3 | Recurring | Corporate - non-U.S. | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	15.10%	46.00%
Level 3 | Recurring | Corporate - non-U.S. | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	7.80%	15.10%
Level 3 | Recurring | Other | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	6.30%	6.30%
Weighted Average Discount Rate Used For Level Three Valuation		9.30%
Discount Rate	4.10%	5.20%
Level 3 | Recurring | Other | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	7.80%	7.50%
Weighted Average Discount Rate Used For Level Three Valuation		9.30%
Discount Rate	4.80%	8.80%
Level 3 | Recurring | Other | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	7.40%	7.20%
Weighted Average Discount Rate Used For Level Three Valuation		9.30%
Discount Rate	4.30%	5.30%
Level 3 | Recurring | Other | Market comparables | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple	5.4	5.4
Level 3 | Recurring | Other | Market comparables | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple	9.1	12.5
Level 3 | Recurring | Other | Market comparables | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple	7.7	9.5
Level 3 | Recurring | Other | Income Approach And Market Comparable Valuation
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	227	381
Level 3 | Nonrecurring | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	787	1,937
Level 3 | Nonrecurring | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	2.70%	5.50%
Discount Rate		6.60%
EBITDA Multiple	4.3	4.3
Level 3 | Nonrecurring | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	11.30%	16.70%
Discount Rate		6.60%
EBITDA Multiple	6.5	5.5
Level 3 | Nonrecurring | Financing receivables and loans held for sale [Member] | Income Approach And Business Enterprise | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	7.30%	8.00%
Discount Rate		6.60%
EBITDA Multiple	6.1	4.8
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis		102
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate		8.50%
WACC		9.30%
Discount Rate		5.70%
Revenue multiple		2.2
EBITDA Multiple		7.1
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate		10.60%
WACC		9.60%
Discount Rate		5.90%
Revenue multiple		12.6
EBITDA Multiple		14.5
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate		10.00%
WACC		9.40%
Discount Rate		5.80%
Revenue multiple		9.4
EBITDA Multiple		11.3
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	343
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	8.00%
EBITDA Multiple	1.8
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	10.00%
EBITDA Multiple	16.2
Level 3 | Nonrecurring | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	9.40%
EBITDA Multiple	7.8
Level 3 | Nonrecurring | Long Lived Assets, Including Real Estate [Member] | Income Approach
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	$ 877	$ 694
Level 3 | Nonrecurring | Long Lived Assets, Including Real Estate [Member] | Income Approach | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	5.50%	5.40%
Discount Rate	2.00%	4.00%
Level 3 | Nonrecurring | Long Lived Assets, Including Real Estate [Member] | Income Approach | Upper Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	15.30%	14.50%
Discount Rate	19.00%	23.00%
Level 3 | Nonrecurring | Long Lived Assets, Including Real Estate [Member] | Income Approach | Weighted Average
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Capitalization Rate	6.30%	7.80%
Discount Rate	6.80%	9.00%