Fair Value (Assets and liabilities measured at fair value on a recurring basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Total fixed maturity securities	$ 39,937	$ 37,577
Equity securities	304	440
Short term investments	1,641	2,215
Separate account business	417	450
Fair Value, Measurements, Recurring [Member]
Total fixed maturity securities	39,937	37,577
Equity securities	304	440
Derivative and other financial instruments, included in Other invested assets	12	27
Short term investments	1,641	2,215
Life settlement contracts, included in Other assets	117	129
Discontinued operations investments, included in Other liabilities		71
Separate account business	417	450
Total assets	42,428	40,909
Derivative financial instruments, included in Other liabilities	(1)	(2)
Total liabilities	(1)	(2)
Fair Value, Measurements, Recurring [Member] | Corporate and other bonds [Member]
Total fixed maturity securities	20,884	21,031
Fair Value, Measurements, Recurring [Member] | States, municipalities and political subdivisions [Member]
Total fixed maturity securities	9,782	7,889
Fair Value, Measurements, Recurring [Member] | Total asset-backed [Member]
Total fixed maturity securities	8,084	7,846
Fair Value, Measurements, Recurring [Member] | Residential mortgage-backed [Member]
Total fixed maturity securities	5,775	6,090
Fair Value, Measurements, Recurring [Member] | Commercial mortgage-backed [Member]
Total fixed maturity securities	1,354	993
Fair Value, Measurements, Recurring [Member] | Other asset-backed [Member]
Total fixed maturity securities	955	763
Fair Value, Measurements, Recurring [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Total fixed maturity securities	493	137
Fair Value, Measurements, Recurring [Member] | Foreign government [Member]
Total fixed maturity securities	636	620
Fair Value, Measurements, Recurring [Member] | Redeemable preferred stock [Member]
Total fixed maturity securities	58	54
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Total fixed maturity securities	548	194
Equity securities	124	288
Derivative and other financial instruments, included in Other invested assets
Short term investments	1,106	1,214
Life settlement contracts, included in Other assets
Discontinued operations investments, included in Other liabilities		11
Separate account business	21	28
Total assets	1,799	1,735
Derivative financial instruments, included in Other liabilities
Total liabilities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate and other bonds [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States, municipalities and political subdivisions [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Total asset-backed [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Residential mortgage-backed [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial mortgage-backed [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other asset-backed [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Total fixed maturity securities	451	76
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign government [Member]
Total fixed maturity securities	92	115
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Redeemable preferred stock [Member]
Total fixed maturity securities	5	3
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Total fixed maturity securities	37,882	35,291
Equity securities	113	126
Derivative and other financial instruments, included in Other invested assets	1
Short term investments	508	974
Life settlement contracts, included in Other assets
Discontinued operations investments, included in Other liabilities		60
Separate account business	373	381
Total assets	38,877	36,832
Derivative financial instruments, included in Other liabilities
Total liabilities
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate and other bonds [Member]
Total fixed maturity securities	20,402	20,407
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States, municipalities and political subdivisions [Member]
Total fixed maturity securities	9,611	7,623
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Total asset-backed [Member]
Total fixed maturity securities	7,230	6,647
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Residential mortgage-backed [Member]
Total fixed maturity securities	5,323	5,323
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial mortgage-backed [Member]
Total fixed maturity securities	1,295	920
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other asset-backed [Member]
Total fixed maturity securities	612	404
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Total fixed maturity securities	42	61
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign government [Member]
Total fixed maturity securities	544	505
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Redeemable preferred stock [Member]
Total fixed maturity securities	53	48
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Total fixed maturity securities	1,507	2,092
Equity securities	67	26
Derivative and other financial instruments, included in Other invested assets	11	27
Short term investments	27	27
Life settlement contracts, included in Other assets	117	129
Discontinued operations investments, included in Other liabilities
Separate account business	23	41
Total assets	1,752	2,342
Derivative financial instruments, included in Other liabilities	(1)	(2)
Total liabilities	(1)	(2)
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate and other bonds [Member]
Total fixed maturity securities	482	624
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States, municipalities and political subdivisions [Member]
Total fixed maturity securities	171	266
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Total asset-backed [Member]
Total fixed maturity securities	854	1,199
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Residential mortgage-backed [Member]
Total fixed maturity securities	452	767
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial mortgage-backed [Member]
Total fixed maturity securities	59	73
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other asset-backed [Member]
Total fixed maturity securities	343	359
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury and obligations of government-sponsored enterprises [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign government [Member]
Total fixed maturity securities
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Redeemable preferred stock [Member]
Total fixed maturity securities		$ 3