Investments (Details 16) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Total number of securities in an unrealized loss position less than 12 months	1,342	3,978
Total number of securities in an unrealized loss position equal to or greater than 12 months	1,587	1,963
Fixed maturity securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	12,368	54,112
Less than 12 Months Gross Unrealized Loss	296	2,247
Equal to or Greater than 12 Months Estimated Fair Value	17,089	20,666
Equal to or Greater than 12 Months Gross Unrealized Loss	1,945	3,266
Total Estimated Fair Value	29,457	74,778
Total Gross Unrealized Loss	2,241	5,513
U.S. corporate securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	3,380	15,642
Less than 12 Months Gross Unrealized Loss	91	590
Equal to or Greater than 12 Months Estimated Fair Value	4,377	5,135
Equal to or Greater than 12 Months Gross Unrealized Loss	425	790
Total Estimated Fair Value	7,757	20,777
Total Gross Unrealized Loss	516	1,380
Foreign corporate securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	3,006	12,618
Less than 12 Months Gross Unrealized Loss	88	639
Equal to or Greater than 12 Months Estimated Fair Value	4,062	5,957
Equal to or Greater than 12 Months Gross Unrealized Loss	290	700
Total Estimated Fair Value	7,068	18,575
Total Gross Unrealized Loss	378	1,339
Foreign government debt securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,935	11,227
Less than 12 Months Gross Unrealized Loss	53	230
Equal to or Greater than 12 Months Estimated Fair Value	864	1,799
Equal to or Greater than 12 Months Gross Unrealized Loss	70	127
Total Estimated Fair Value	2,799	13,026
Total Gross Unrealized Loss	123	357
RMBS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	531	4,040
Less than 12 Months Gross Unrealized Loss	37	547
Equal to or Greater than 12 Months Estimated Fair Value	4,822	4,724
Equal to or Greater than 12 Months Gross Unrealized Loss	845	1,189
Total Estimated Fair Value	5,353	8,764
Total Gross Unrealized Loss	882	1,736
U.S. Treasury, agency and government guaranteed securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,475	2,611
Less than 12 Months Gross Unrealized Loss	5	1
Equal to or Greater than 12 Months Estimated Fair Value	0	50
Equal to or Greater than 12 Months Gross Unrealized Loss	0	1
Total Estimated Fair Value	1,475	2,661
Total Gross Unrealized Loss	5	2
CMBS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	524	2,825
Less than 12 Months Gross Unrealized Loss	10	135
Equal to or Greater than 12 Months Estimated Fair Value	829	678
Equal to or Greater than 12 Months Gross Unrealized Loss	74	91
Total Estimated Fair Value	1,353	3,503
Total Gross Unrealized Loss	84	226
ABS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,363	4,972
Less than 12 Months Gross Unrealized Loss	11	103
Equal to or Greater than 12 Months Estimated Fair Value	1,783	1,316
Equal to or Greater than 12 Months Gross Unrealized Loss	163	214
Total Estimated Fair Value	3,146	6,288
Total Gross Unrealized Loss	174	317
State and political subdivision securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	154	177
Less than 12 Months Gross Unrealized Loss	1	2
Equal to or Greater than 12 Months Estimated Fair Value	352	1,007
Equal to or Greater than 12 Months Gross Unrealized Loss	78	154
Total Estimated Fair Value	506	1,184
Total Gross Unrealized Loss	79	156
Equity Securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	281	785
Less than 12 Months Gross Unrealized Loss	35	126
Equal to or Greater than 12 Months Estimated Fair Value	437	375
Equal to or Greater than 12 Months Gross Unrealized Loss	164	173
Total Estimated Fair Value	718	1,160
Total Gross Unrealized Loss	199	299
Common Stock
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	271	581
Less than 12 Months Gross Unrealized Loss	35	96
Equal to or Greater than 12 Months Estimated Fair Value	109	5
Equal to or Greater than 12 Months Gross Unrealized Loss	7	1
Total Estimated Fair Value	380	586
Total Gross Unrealized Loss	42	97
Non-redeemable preferred stock [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	10	204
Less than 12 Months Gross Unrealized Loss	0	30
Equal to or Greater than 12 Months Estimated Fair Value	328	370
Equal to or Greater than 12 Months Gross Unrealized Loss	157	172
Total Estimated Fair Value	338	574
Total Gross Unrealized Loss	157	202