Investments (Details 17) (USD $) In Millions, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	$ 344,791	$ 329,811
Cost or Amortized Cost	2,838	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	344,791	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	2,838	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	28,323	72,103
Cost or Amortized Cost	483	852
Gross Unrealized Loss	1,157	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	4.00%	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	7.00%	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	3,375	8,188
Cost or Amortized Cost	434	607
Gross Unrealized Loss	1,084	2,617
Gross Unrealized Loss	166	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	9,978	49,249
Cost or Amortized Cost	195	714
Gross Unrealized Loss	140	1,346
Gross Unrealized Loss	11	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	914	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	77	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	430	4,736
Cost or Amortized Cost	102	376
Gross Unrealized Loss	111	1,332
Gross Unrealized Loss	28	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	66	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	32	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	1,265	4,104
Cost or Amortized Cost	37	22
Gross Unrealized Loss	37	279
Gross Unrealized Loss	4	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	116	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	16	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	147	1,049
Cost or Amortized Cost	0	8
Gross Unrealized Loss	49	349
Gross Unrealized Loss	0	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	40	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	0	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	1,209	1,160
Cost or Amortized Cost	26	18
Gross Unrealized Loss	50	55
Gross Unrealized Loss	2	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	175	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	9	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	233	288
Cost or Amortized Cost	42	0
Gross Unrealized Loss	69	93
Gross Unrealized Loss	14	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	40	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	2	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	15,871	17,590
Cost or Amortized Cost	225	98
Gross Unrealized Loss	930	1,216
Gross Unrealized Loss	16	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	1,303	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	37	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	2,565	2,115
Cost or Amortized Cost	290	223
Gross Unrealized Loss	855	843
Gross Unrealized Loss	$ 124	$ 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	166	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	15	20