Investments (Details 17) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Aging of Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Amortized Cost	$ 338,871	$ 329,811
Cost or Amortized Cost	2,973	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	338,871	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	2,973	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	54,564	72,103
Cost or Amortized Cost	668	852
Gross Unrealized Loss	1,813	2,896
Gross Unrealized Loss	56	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	8.00%	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	5,199	8,188
Cost or Amortized Cost	450	607
Gross Unrealized Loss	1,669	2,617
Gross Unrealized Loss	165	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	37.00%	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	30,061	49,249
Cost or Amortized Cost	333	714
Gross Unrealized Loss	340	1,346
Gross Unrealized Loss	24	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	2,142	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	118	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	1,073	4,736
Cost or Amortized Cost	72	376
Gross Unrealized Loss	272	1,332
Gross Unrealized Loss	19	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	125	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	33	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	2,582	4,104
Cost or Amortized Cost	84	22
Gross Unrealized Loss	110	279
Gross Unrealized Loss	8	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	276	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	10	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	337	1,049
Cost or Amortized Cost	43	8
Gross Unrealized Loss	98	349
Gross Unrealized Loss	12	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	51	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	2	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	7,520	1,160
Cost or Amortized Cost	148	18
Gross Unrealized Loss	354	55
Gross Unrealized Loss	19	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	567	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	32	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	1,256	288
Cost or Amortized Cost	112	0
Gross Unrealized Loss	397	93
Gross Unrealized Loss	34	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	72	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	7	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	14,401	17,590
Cost or Amortized Cost	103	98
Gross Unrealized Loss	1,009	1,216
Gross Unrealized Loss	5	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	1,314	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	22	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	2,533	2,115
Cost or Amortized Cost	223	223
Gross Unrealized Loss	902	843
Gross Unrealized Loss	$ 100	$ 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	180	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