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	301	808
Total number of securities in an unrealized loss position equal to or greater than 12 months	434	479
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	1,694	4,845
Less than 12 Months Gross Unrealized Loss	25	272
Equal to or Greater than 12 Months Estimated Fair Value	2,456	2,683
Equal to or Greater than 12 Months Gross Unrealized Loss	305	505
Total Estimated Fair Value	4,150	7,528
Total Gross Unrealized Loss	330	777
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	613	1,699
Less than 12 Months Gross Unrealized Loss	13	71
Equal to or Greater than 12 Months Estimated Fair Value	755	786
Equal to or Greater than 12 Months Gross Unrealized Loss	83	158
Total Estimated Fair Value	1,368	2,485
Total Gross Unrealized Loss	96	229
US Treasury and Government [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	400	118
Less than 12 Months Gross Unrealized Loss	0	0
Equal to or Greater than 12 Months Estimated Fair Value	0	20
Equal to or Greater than 12 Months Gross Unrealized Loss	0	1
Total Estimated Fair Value	400	138
Total Gross Unrealized Loss	0	1
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	281	1,213
Less than 12 Months Gross Unrealized Loss	7	68
Equal to or Greater than 12 Months Estimated Fair Value	241	162
Equal to or Greater than 12 Months Gross Unrealized Loss	27	46
Total Estimated Fair Value	522	1,375
Total Gross Unrealized Loss	34	114
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	34	784
Less than 12 Months Gross Unrealized Loss	1	114
Equal to or Greater than 12 Months Estimated Fair Value	938	972
Equal to or Greater than 12 Months Gross Unrealized Loss	139	200
Total Estimated Fair Value	972	1,756
Total Gross Unrealized Loss	140	314
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	38	152
Less than 12 Months Gross Unrealized Loss	1	4
Equal to or Greater than 12 Months Estimated Fair Value	120	111
Equal to or Greater than 12 Months Gross Unrealized Loss	9	12
Total Estimated Fair Value	158	263
Total Gross Unrealized Loss	10	16
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	39	6
Less than 12 Months Gross Unrealized Loss	1	0
Equal to or Greater than 12 Months Estimated Fair Value	75	367
Equal to or Greater than 12 Months Gross Unrealized Loss	26	58
Total Estimated Fair Value	114	373
Total Gross Unrealized Loss	27	58
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	180	803
Less than 12 Months Gross Unrealized Loss	0	12
Equal to or Greater than 12 Months Estimated Fair Value	327	261
Equal to or Greater than 12 Months Gross Unrealized Loss	21	30
Total Estimated Fair Value	507	1,064
Total Gross Unrealized Loss	21	42
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	109	70
Less than 12 Months Gross Unrealized Loss	2	3
Equal to or Greater than 12 Months Estimated Fair Value	0	4
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
Total Estimated Fair Value	109	74
Total Gross Unrealized Loss	2	3
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	30	67
Less than 12 Months Gross Unrealized Loss	3	29
Equal to or Greater than 12 Months Estimated Fair Value	60	59
Equal to or Greater than 12 Months Gross Unrealized Loss	25	28
Total Estimated Fair Value	90	126
Total Gross Unrealized Loss	28	57
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	3	32
Less than 12 Months Gross Unrealized Loss	0	16
Equal to or Greater than 12 Months Estimated Fair Value	55	59
Equal to or Greater than 12 Months Gross Unrealized Loss	24	28
Total Estimated Fair Value	58	91
Total Gross Unrealized Loss	24	44
Common 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	27	35
Less than 12 Months Gross Unrealized Loss	3	13
Equal to or Greater than 12 Months Estimated Fair Value	5	0
Equal to or Greater than 12 Months Gross Unrealized Loss	1	0
Total Estimated Fair Value	32	35
Total Gross Unrealized Loss	4	13