Investments (Details 17) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	$ 332,981	$ 329,811
Cost or Amortized Cost	3,063	3,208
Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	332,981	329,811
Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Cost or Amortized Cost	3,063	3,208
Less than 20% [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	57,508	72,103
Cost or Amortized Cost	535	852
Gross Unrealized Loss	1,963	2,896
Gross Unrealized Loss	33	76
Less than 20% [Member] | Fixed maturity securities [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	3.00%	4.00%
Less than 20% [Member] | Equity Securities [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	6.00%	9.00%
20% or more [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	5,493	8,188
Cost or Amortized Cost	381	607
Gross Unrealized Loss	1,770	2,617
Gross Unrealized Loss	144	223
20% or more [Member] | Fixed maturity securities [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	32.00%	32.00%
20% or more [Member] | Equity Securities [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	38.00%	37.00%
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	27,651	49,249
Cost or Amortized Cost	139	714
Gross Unrealized Loss	441	1,346
Gross Unrealized Loss	5	64
Less than six months [Member] | Less than 20% [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	2,367	3,260
Less than six months [Member] | Less than 20% [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	64	154
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	971	4,736
Cost or Amortized Cost	46	376
Gross Unrealized Loss	258	1,332
Gross Unrealized Loss	14	123
Less than six months [Member] | 20% or more [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	118	320
Less than six months [Member] | 20% or more [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	16	42
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	11,280	4,104
Cost or Amortized Cost	233	22
Gross Unrealized Loss	367	279
Gross Unrealized Loss	17	2
Six months or greater but less than nine months [Member] | Less than 20% [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	820	375
Six months or greater but less than nine months [Member] | Less than 20% [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	50	19
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	1,549	1,049
Cost or Amortized Cost	112	8
Gross Unrealized Loss	452	349
Gross Unrealized Loss	32	4
Six months or greater but less than nine months [Member] | 20% or more [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	84	63
Six months or greater but less than nine months [Member] | 20% or more [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	7	3
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	3,306	1,160
Cost or Amortized Cost	49	18
Gross Unrealized Loss	149	55
Gross Unrealized Loss	3	2
Nine months or greater but less than twelve months [Member] | Less than 20% [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	292	143
Nine months or greater but less than twelve months [Member] | Less than 20% [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	17	8
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	791	288
Cost or Amortized Cost	0	0
Gross Unrealized Loss	237	93
Gross Unrealized Loss	0	0
Nine months or greater but less than twelve months [Member] | 20% or more [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	43	14
Nine months or greater but less than twelve months [Member] | 20% or more [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	1	0
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	15,271	17,590
Cost or Amortized Cost	114	98
Gross Unrealized Loss	1,006	1,216
Gross Unrealized Loss	8	8
Twelve months or greater [Member] | Less than 20% [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	1,340	1,523
Twelve months or greater [Member] | Less than 20% [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	20	24
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	2,182	2,115
Cost or Amortized Cost	223	223
Gross Unrealized Loss	823	843
Gross Unrealized Loss	$ 98	$ 96
Twelve months or greater [Member] | 20% or more [Member] | Fixed maturity securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	162	167
Twelve months or greater [Member] | 20% or more [Member] | Equity Securities [Member]
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Number of Securities	19	20