Fair Value Measurements (Level 3 Measurements) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	$ 730	$ 1,460
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,968	2,816
Individually Insignificant Recurring Fair Value Measurements	185	327
Individually Insignificant NonRecurring Fair Value Measurements	275	571
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	1,596	2,986
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	354	690
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	192	1,088
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	947	898
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [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%	1.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [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	8.90%	13.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		6.50%
Weighted Average Discount Rate Used For Level Three Valuation	5.00%
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	6,868	6,854
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [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	1.30%	1.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [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	9.50%	10.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed Securities [Member] | Income Approach Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		3.70%
Weighted Average Discount Rate Used For Level Three Valuation	3.80%
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	776	819
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [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	1.40%	1.40%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [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	46.00%	46.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Income Approach Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		15.10%
Weighted Average Discount Rate Used For Level Three Valuation	15.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Market Comparables Valuation Technique [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		6.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Market Comparables Valuation Technique [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		7.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Market Comparables Valuation Technique [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Capitalization Rate Used For Level Three Valuation		7.20%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	278	381
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable Valuation Techniques [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	3.90%	5.20%
Fair Value Inputs, Revenue Multiple	1.7
Range Capitalization Rate Used For Level Three Valuation	7.30%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable Valuation Techniques [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	5.60%	8.80%
Fair Value Inputs, Revenue Multiple	1.7
Range Capitalization Rate Used For Level Three Valuation	8.80%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		5.30%
Fair Value Inputs, Revenue Multiple	1.7
Range Capitalization Rate Used For Level Three Valuation	7.60%
Weighted Average Discount Rate Used For Level Three Valuation	4.80%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable 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	5.4	5.4
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable 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	8.9	12.5
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other 1 [Member] | Income Approach And Market Comparable 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	6.9	9.5
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State And Municipal Debt [Member] | Income Approach Valuation Techniques [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	469
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State And Municipal Debt [Member] | Income Approach Valuation Techniques [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	1.80%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State And Municipal Debt [Member] | Income Approach Valuation Techniques [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	6.00%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State And Municipal Debt [Member] | Income Approach Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	3.30%
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	995	1,937
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] | Lower Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		6.60%
Range Capitalization Rate Used For Level Three Valuation	2.70%	5.50%
Weighted Average Cost Of Capital Used For Level Three Valuation	19.00%
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] | Upper Limit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		6.60%
Range Capitalization Rate Used For Level Three Valuation	11.30%	16.70%
Weighted Average Cost Of Capital Used For Level Three Valuation	19.00%
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] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		6.60%
Weighted Average Cost Of Capital Used For Level Three Valuation	19.00%
Weighted Average Capitalization Rate Used For Level Three Valuation	6.50%	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	4.3
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	6.5	5.5
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	5.9	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		102
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation Techniques [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		5.70%
Fair Value Inputs, Revenue Multiple		2.2
Range Capitalization Rate Used For Level Three Valuation		8.50%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.30%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation Techniques [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		5.90%
Fair Value Inputs, Revenue Multiple		12.6
Range Capitalization Rate Used For Level Three Valuation		10.60%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.60%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation		5.80%
Fair Value Inputs, Revenue Multiple		9.4
Range Capitalization Rate Used For Level Three Valuation		10.00%
Weighted Average Cost Of Capital Used For Level Three Valuation		9.40%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable 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		7.1
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable 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		14.5
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable 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		11.3
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise Valuation [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value Assets Measured On Non Recurring Basis	137
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise Valuation [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	8.00%
Fair Value Inputs, Revenue Multiple	2.9
EBITDA Multiple Used For Level Three Valuation	6.0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise Valuation [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	10.00%
Fair Value Inputs, Revenue Multiple	2.9
EBITDA Multiple Used For Level Three Valuation	9.0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach And Market Comparable And Business Enterprise Valuation [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	8.50%
Fair Value Inputs, Revenue Multiple	2.9
EBITDA Multiple Used For Level Three Valuation	9.0
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	$ 5	$ 694
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [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	4.00%	4.00%
Range Capitalization Rate Used For Level Three Valuation	9.40%	5.40%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [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	19.00%	23.00%
Range Capitalization Rate Used For Level Three Valuation	15.30%	14.50%
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach Valuation Techniques [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Range Discount Rate Used For Level Three Valuation	8.30%	9.00%
Weighted Average Capitalization Rate Used For Level Three Valuation	12.00%	7.80%