Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 42,852	$ 43,073
Fair value of assets, measured on a recurring basis	42,852	43,073
Liabilities, Fair Value Disclosure, Recurring	(1)
Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	19,154	20,898
States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	12,469	11,557
Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	5,146	4,971
Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2,158	2,063
Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,230	955
Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	8,534	7,989
U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	30	144
Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	471	543
Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	42	102
Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	40,700	41,233
Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	211	185
Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	44	54
Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,811	1,332
Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	86	88
Separate account business [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		181
Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	(1)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	1,477	1,179
Fair value of assets, measured on a recurring basis	1,477	1,179
Liabilities, Fair Value Disclosure, Recurring
Fair Value, Inputs, Level 1 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	33	33
Fair Value, Inputs, Level 1 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	27	116
Fair Value, Inputs, Level 1 [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	47	81
Fair Value, Inputs, Level 1 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	30	45
Fair Value, Inputs, Level 1 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	137	275
Fair Value, Inputs, Level 1 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	141	126
Fair Value, Inputs, Level 1 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,199	769
Fair Value, Inputs, Level 1 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Separate account business [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		9
Fair Value, Inputs, Level 1 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	40,120	40,591
Fair value of assets, measured on a recurring basis	40,120	40,591
Liabilities, Fair Value Disclosure, Recurring	(1)
Fair Value, Inputs, Level 2 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	18,948	20,661
Fair Value, Inputs, Level 2 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	12,389	11,486
Fair Value, Inputs, Level 2 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	4,986	4,640
Fair Value, Inputs, Level 2 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2,061	1,912
Fair Value, Inputs, Level 2 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	588	509
Fair Value, Inputs, Level 2 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	7,635	7,061
Fair Value, Inputs, Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	3	28
Fair Value, Inputs, Level 2 [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	424	462
Fair Value, Inputs, Level 2 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	12	57
Fair Value, Inputs, Level 2 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	39,411	39,755
Fair Value, Inputs, Level 2 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	53	48
Fair Value, Inputs, Level 2 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	44	54
Fair Value, Inputs, Level 2 [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	612	563
Fair Value, Inputs, Level 2 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 2 [Member] | Separate account business [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		171
Fair Value, Inputs, Level 2 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring	(1)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets, Fair Value Disclosure	1,255	1,303
Fair value of assets, measured on a recurring basis	1,255	1,303
Liabilities, Fair Value Disclosure, Recurring
Fair Value, Inputs, Level 3 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	173	204
Fair Value, Inputs, Level 3 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	80	71
Fair Value, Inputs, Level 3 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	160	331
Fair Value, Inputs, Level 3 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	97	151
Fair Value, Inputs, Level 3 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	642	446
Fair Value, Inputs, Level 3 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	899	928
Fair Value, Inputs, Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 3 [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 3 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 3 [Member] | Fixed maturity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,152	1,203
Fair Value, Inputs, Level 3 [Member] | Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	17	11
Fair Value, Inputs, Level 3 [Member] | Other invested assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 3 [Member] | Short-term investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis
Fair Value, Inputs, Level 3 [Member] | Life settlement contracts, included in Other assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	86	88
Fair Value, Inputs, Level 3 [Member] | Separate account business [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		1
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities, Fair Value Disclosure, Recurring