Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	$ 41,274	$ 42,633
Equity securities	199	249
Other invested assets	55	59
Short term investments	1,475	1,832
Separate account business	213	312
Derivative financial instruments, included in Other liabilities	(1)	(3)
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	41,274	42,633
Equity securities	199	249
Other invested assets	55	59
Short term investments	1,422	1,792
Life settlement contracts, included in Other assets	90	100
Separate account business	213	312
Total assets	43,253	45,145
Derivative financial instruments, included in Other liabilities	(1)	(3)
Total liabilities	(1)	(3)
Fair Value, Measurements, Recurring [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	21,183	22,236
Fair Value, Measurements, Recurring [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	11,459	10,783
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,819	5,920
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	2,017	1,822
Fair Value, Measurements, Recurring [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	956	952
Fair Value, Measurements, Recurring [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	7,792	8,694
Fair Value, Measurements, Recurring [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	173	182
Fair Value, Measurements, Recurring [Member] | Foreign government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	561	613
Fair Value, Measurements, Recurring [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	106	125
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	300	344
Equity securities	135	117
Other invested assets
Short term investments	992	987
Life settlement contracts, included in Other assets
Separate account business	12	4
Total assets	1,439	1,452
Derivative financial instruments, included in Other liabilities
Total liabilities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	27	6
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	144	158
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	81	140
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	48	40
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	39,708	41,038
Equity securities	51	98
Other invested assets	55	58
Short term investments	430	799
Life settlement contracts, included in Other assets
Separate account business	199	306
Total assets	40,443	42,299
Derivative financial instruments, included in Other liabilities	(1)	(2)
Total liabilities	(1)	(2)
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	20,945	22,011
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	11,364	10,687
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	4,449	5,507
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	1,860	1,693
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	523	584
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	6,832	7,784
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	29	24
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	480	473
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	58	59
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	1,266	1,251
Equity securities	13	34
Other invested assets		1
Short term investments		6
Life settlement contracts, included in Other assets	90	100
Separate account business	2	2
Total assets	1,371	1,394
Derivative financial instruments, included in Other liabilities		(1)
Total liabilities		(1)
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate and other bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	211	219
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	95	96
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	370	413
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	157	129
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	433	368
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Total asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities	960	910
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity securities		$ 26