Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
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	625	752
Total number of securities in an unrealized loss position equal to or greater than 12 months	292	333
Fixed maturity securities
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	$ 5,449	$ 7,624
Less than 12 Months Gross Unrealized Loss	139	129
Equal to or Greater than 12 Months Estimated Fair Value	1,253	1,853
Equal to or Greater than 12 Months Gross Unrealized Loss	135	139
U.S. corporate
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,094	1,346
Less than 12 Months Gross Unrealized Loss	37	45
Equal to or Greater than 12 Months Estimated Fair Value	428	685
Equal to or Greater than 12 Months Gross Unrealized Loss	69	74
Foreign corporate
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,033	1,031
Less than 12 Months Gross Unrealized Loss	73	49
Equal to or Greater than 12 Months Estimated Fair Value	117	133
Equal to or Greater than 12 Months Gross Unrealized Loss	11	9
U.S. Treasury and agency
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,929	4,067
Less than 12 Months Gross Unrealized Loss	12	5
Equal to or Greater than 12 Months Estimated Fair Value	0	163
Equal to or Greater than 12 Months Gross Unrealized Loss	0	2
RMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	926	684
Less than 12 Months Gross Unrealized Loss	13	26
Equal to or Greater than 12 Months Estimated Fair Value	485	530
Equal to or Greater than 12 Months Gross Unrealized Loss	51	42
State and political subdivision
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	14	11
Less than 12 Months Gross Unrealized Loss	1	0
Equal to or Greater than 12 Months Estimated Fair Value	20	24
Equal to or Greater than 12 Months Gross Unrealized Loss	0	1
CMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	114	124
Less than 12 Months Gross Unrealized Loss	1	1
Equal to or Greater than 12 Months Estimated Fair Value	22	78
Equal to or Greater than 12 Months Gross Unrealized Loss	0	2
ABS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	325	334
Less than 12 Months Gross Unrealized Loss	1	2
Equal to or Greater than 12 Months Estimated Fair Value	178	231
Equal to or Greater than 12 Months Gross Unrealized Loss	4	8
Foreign government
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	14	27
Less than 12 Months Gross Unrealized Loss	1	1
Equal to or Greater than 12 Months Estimated Fair Value	3	9
Equal to or Greater than 12 Months Gross Unrealized Loss	0	1
Equity securities
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	28	39
Less than 12 Months Gross Unrealized Loss	5	4
Equal to or Greater than 12 Months Estimated Fair Value	43	44
Equal to or Greater than 12 Months Gross Unrealized Loss	7	6
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	16	11
Less than 12 Months Gross Unrealized Loss	3	3
Equal to or Greater than 12 Months Estimated Fair Value	0	0
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
Non-redeemable preferred stock
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	12	28
Less than 12 Months Gross Unrealized Loss	2	1
Equal to or Greater than 12 Months Estimated Fair Value	43	44
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 7	$ 6