Fair Value Measurements (Significant Unobservable Input) (Details) - Fair Value, Inputs, Level 3 - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value, Measurement Recurring Basis, Asset Value	$ 2,664	$ 2,594
Fair Value, Measurements, Recurring
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair Value, Measurement Recurring Basis, Asset Value	3,855	3,948	$ 3,997	$ 4,130	$ 4,088	$ 3,878
Individually Insignificant Recurring Fair Value Measurements	5	30
Fair Value, Measurements, Recurring | Domestic Corporate Debt Securities [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	$ 855	$ 917
Fair Value, Measurements, Recurring | Domestic Corporate Debt Securities [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	1.80%	1.50%
Fair Value, Measurements, Recurring | Domestic Corporate Debt Securities [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	11.00%	14.80%
Fair Value, Measurements, Recurring | Domestic Corporate Debt Securities [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	7.00%	6.60%
Fair Value, Measurements, Recurring | Asset-backed Securities [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	$ 76	$ 102
Fair Value, Measurements, Recurring | Asset-backed Securities [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.00%	4.30%
Fair Value, Measurements, Recurring | Asset-backed Securities [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.50%	9.00%
Fair Value, Measurements, Recurring | Asset-backed Securities [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.40%	2.60%
Fair Value, Measurements, Recurring | Foreign Corporate Debt Securities [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	$ 227	$ 278
Fair Value, Measurements, Recurring | Foreign Corporate Debt Securities [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	6.00%	3.30%
Fair Value, Measurements, Recurring | Foreign Corporate Debt Securities [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	14.00%	14.00%
Fair Value, Measurements, Recurring | Foreign Corporate Debt Securities [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	7.40%	6.50%
Fair Value, Measurements, Recurring | State And Municipal Debt Securities [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	$ 17	$ 17
Fair Value, Measurements, Recurring | State And Municipal Debt Securities [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.20%	4.90%
Fair Value, Measurements, Recurring | State And Municipal Debt Securities [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.20%	4.90%
Fair Value, Measurements, Recurring | State And Municipal Debt Securities [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	5.20%	4.90%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value measurments - nonrecurring	$ 297	$ 657
Individually Insignificant NonRecurring Fair Value Measurements	$ 127	6
Fair Value, Measurements, Nonrecurring [Member] | Market Comparables [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Equity multiple	40.00%
Fair Value, Measurements, Nonrecurring [Member] | Market Comparables [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Equity multiple	70.00%
Fair Value, Measurements, Nonrecurring [Member] | Market Comparables [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Equity multiple	60.00%
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value measurments - nonrecurring	$ 22,483
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	0.10%
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	8.00%
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	6.70%
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Business Enterprise Value Valuation Technique [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value measurments - nonrecurring		$ 0
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Business Enterprise Value Valuation Technique [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		0
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Business Enterprise Value Valuation Technique [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		0
Fair Value, Measurements, Nonrecurring [Member] | Financing receivables and loans held for sale [Member] | Business Enterprise Value Valuation Technique [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		0
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate		8.00%
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate		10.00%
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate		9.40%
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Market Comparables [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		1.8
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Market Comparables [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		5.2
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Market Comparables [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
EBITDA Multiple		4.8
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach, Business Enterprise, Market comparables [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure	$ 1,867
Fair Value, Measurements, Nonrecurring [Member] | Cost and equity method investments [Member] | Income Approach, Market Comparables [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Investments, Fair Value Disclosure		$ 309
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value measurments - nonrecurring	$ 17	$ 664
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach [Member] | Lower Limit
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	2.00%	2.00%
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach [Member] | Maximum [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	10.80%	10.80%
Fair Value, Measurements, Nonrecurring [Member] | Long Lived Assets, Including Real Estate [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Discount Rate	6.80%	6.70%