Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
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	1,997	2,211
Total number of securities in an unrealized loss position equal to or greater than 12 months	642	469
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	$ 27,348	$ 36,223
Less than 12 Months Gross Unrealized Loss	823	1,820
Equal to or Greater than 12 Months Estimated Fair Value	7,832	5,505
Equal to or Greater than 12 Months Gross Unrealized Loss	542	758
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	8,950	8,512
Less than 12 Months Gross Unrealized Loss	260	426
Equal to or Greater than 12 Months Estimated Fair Value	2,251	1,948
Equal to or Greater than 12 Months Gross Unrealized Loss	161	267
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	3,933	10,077
Less than 12 Months Gross Unrealized Loss	6	687
Equal to or Greater than 12 Months Estimated Fair Value	982	33
Equal to or Greater than 12 Months Gross Unrealized Loss	13	7
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	7,052	4,217
Less than 12 Months Gross Unrealized Loss	397	176
Equal to or Greater than 12 Months Estimated Fair Value	1,165	952
Equal to or Greater than 12 Months Gross Unrealized Loss	114	109
RMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	3,141	8,194
Less than 12 Months Gross Unrealized Loss	63	291
Equal to or Greater than 12 Months Estimated Fair Value	1,900	1,675
Equal to or Greater than 12 Months Gross Unrealized Loss	160	227
CMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	772	2,022
Less than 12 Months Gross Unrealized Loss	20	74
Equal to or Greater than 12 Months Estimated Fair Value	461	221
Equal to or Greater than 12 Months Gross Unrealized Loss	13	15
ABS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	3,147	1,701
Less than 12 Months Gross Unrealized Loss	45	28
Equal to or Greater than 12 Months Estimated Fair Value	732	530
Equal to or Greater than 12 Months Gross Unrealized Loss	37	88
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	26	737
Less than 12 Months Gross Unrealized Loss	0	44
Equal to or Greater than 12 Months Estimated Fair Value	76	92
Equal to or Greater than 12 Months Gross Unrealized Loss	6	32
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	327	763
Less than 12 Months Gross Unrealized Loss	32	94
Equal to or Greater than 12 Months Estimated Fair Value	265	54
Equal to or Greater than 12 Months Gross Unrealized Loss	38	13
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	130	259
Less than 12 Months Gross Unrealized Loss	26	44
Equal to or Greater than 12 Months Estimated Fair Value	140	125
Equal to or Greater than 12 Months Gross Unrealized Loss	30	36
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	98	37
Less than 12 Months Gross Unrealized Loss	26	3
Equal to or Greater than 12 Months Estimated Fair Value	1	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	32	222
Less than 12 Months Gross Unrealized Loss	0	41
Equal to or Greater than 12 Months Estimated Fair Value	139	125
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 30	$ 36