Investments (Details 17) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	$ 334,009	$ 317,617
Cost or Amortized Cost	3,227	3,621
Less than six months [Member] | Fixed maturity securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	2,871	5,320
Less than six months [Member] | Fixed maturity securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	290	121
Less than six months [Member] | Equity Securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	168	106
Less than six months [Member] | Equity Securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	54	33
Less than six months [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	50,785	105,301
Cost or Amortized Cost	571	247
Gross Unrealized Loss	1,365	2,348
Gross Unrealized Loss	36	10
Less than six months [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	5,026	1,403
Cost or Amortized Cost	304	94
Gross Unrealized Loss	1,377	368
Gross Unrealized Loss	89	22
Six months or greater but less than nine months [Member] | Fixed maturity securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	200	104
Six months or greater but less than nine months [Member] | Fixed maturity securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	23	29
Six months or greater but less than nine months [Member] | Equity Securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	7	3
Six months or greater but less than nine months [Member] | Equity Securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	3	2
Six months or greater but less than nine months [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	1,747	1,125
Cost or Amortized Cost	10	29
Gross Unrealized Loss	68	29
Gross Unrealized Loss	1	5
Six months or greater but less than nine months [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	349	376
Cost or Amortized Cost	0	65
Gross Unrealized Loss	106	102
Gross Unrealized Loss	0	16
Nine months or greater but less than twelve months [Member] | Fixed maturity securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	1,126	50
Nine months or greater but less than twelve months [Member] | Fixed maturity securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	9	9
Nine months or greater but less than twelve months [Member] | Equity Securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	14	3
Nine months or greater but less than twelve months [Member] | Equity Securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	9	2
Nine months or greater but less than twelve months [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	13,543	371
Cost or Amortized Cost	46	6
Gross Unrealized Loss	367	28
Gross Unrealized Loss	4	0
Nine months or greater but less than twelve months [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	147	89
Cost or Amortized Cost	1	47
Gross Unrealized Loss	41	27
Gross Unrealized Loss	1	16
Twelve months or greater [Member] | Fixed maturity securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	971	1,245
Twelve months or greater [Member] | Fixed maturity securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	181	311
Twelve months or greater [Member] | Equity Securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	11	35
Twelve months or greater [Member] | Equity Securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	13	14
Twelve months or greater [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	11,858	21,627
Cost or Amortized Cost	125	518
Gross Unrealized Loss	1,018	1,863
Gross Unrealized Loss	12	56
Twelve months or greater [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	2,355	5,546
Cost or Amortized Cost	223	340
Gross Unrealized Loss	908	1,815
Gross Unrealized Loss	85	116
Fixed maturity securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Gross unrealized loss, percentage of amortized cost fixed maturity securities	4.00%	3.00%
Equity Securities [Member] | Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Gross unrealized loss, percentage of cost equity securities	7.00%	9.00%
Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	77,933	128,424
Cost or Amortized Cost	752	800
Gross Unrealized Loss	2,818	4,268
Gross Unrealized Loss	53	71
Fixed maturity securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Gross unrealized loss, percentage of amortized cost fixed maturity securities	31.00%	31.00%
Equity Securities [Member] | 20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Gross unrealized loss, percentage of cost equity securities	33.00%	31.00%
20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	7,877	7,414
Cost or Amortized Cost	528	546
Gross Unrealized Loss	2,432	2,312
Gross Unrealized Loss	175	170
Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	334,009	317,617
Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Cost or Amortized Cost	$ 3,227	$ 3,621