Investments (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 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	1,941	3,978
Total number of securities in an unrealized loss position equal to or greater than 12 months	1,335	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	13,721	54,112
Less than 12 Months Gross Unrealized Loss	293	2,247
Equal to or Greater than 12 Months Estimated Fair Value	13,447	20,666
Equal to or Greater than 12 Months Gross Unrealized Loss	1,455	3,266
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	3,799	15,642
Less than 12 Months Gross Unrealized Loss	88	590
Equal to or Greater than 12 Months Estimated Fair Value	3,695	5,135
Equal to or Greater than 12 Months Gross Unrealized Loss	342	790
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	2,783	12,618
Less than 12 Months Gross Unrealized Loss	96	639
Equal to or Greater than 12 Months Estimated Fair Value	2,873	5,957
Equal to or Greater than 12 Months Gross Unrealized Loss	180	700
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	1,431	11,227
Less than 12 Months Gross Unrealized Loss	22	230
Equal to or Greater than 12 Months Estimated Fair Value	543	1,799
Equal to or Greater than 12 Months Gross Unrealized Loss	49	127
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	735	4,040
Less than 12 Months Gross Unrealized Loss	31	547
Equal to or Greater than 12 Months Estimated Fair Value	4,098	4,724
Equal to or Greater than 12 Months Gross Unrealized Loss	633	1,189
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	1,951	2,611
Less than 12 Months Gross Unrealized Loss	11	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
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	842	2,825
Less than 12 Months Gross Unrealized Loss	11	135
Equal to or Greater than 12 Months Estimated Fair Value	577	678
Equal to or Greater than 12 Months Gross Unrealized Loss	46	91
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	1,920	4,972
Less than 12 Months Gross Unrealized Loss	30	103
Equal to or Greater than 12 Months Estimated Fair Value	1,410	1,316
Equal to or Greater than 12 Months Gross Unrealized Loss	139	214
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	260	177
Less than 12 Months Gross Unrealized Loss	4	2
Equal to or Greater than 12 Months Estimated Fair Value	251	1,007
Equal to or Greater than 12 Months Gross Unrealized Loss	66	154
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	201	785
Less than 12 Months Gross Unrealized Loss	18	126
Equal to or Greater than 12 Months Estimated Fair Value	309	375
Equal to or Greater than 12 Months Gross Unrealized Loss	141	173
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	201	581
Less than 12 Months Gross Unrealized Loss	18	96
Equal to or Greater than 12 Months Estimated Fair Value	14	5
Equal to or Greater than 12 Months Gross Unrealized Loss	1	1
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	0	204
Less than 12 Months Gross Unrealized Loss	0	30
Equal to or Greater than 12 Months Estimated Fair Value	295	370
Equal to or Greater than 12 Months Gross Unrealized Loss	140	172