Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) $ in Millions	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
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	2,579	6,366
Total number of securities in an unrealized loss position equal to or greater than 12 months	1,871	1,489
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	$ 29,579	$ 92,421
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,048	3,475
Equal to or Greater than 12 Months Estimated Fair Value	19,344	15,799
Equal to or Greater than 12 Months Gross Unrealized Loss	1,757	1,970
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	5,559	27,526
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	274	1,629
Equal to or Greater than 12 Months Estimated Fair Value	4,612	3,762
Equal to or Greater than 12 Months Gross Unrealized Loss	447	626
U.S. government 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	6,305	19,628
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24	222
Equal to or Greater than 12 Months Estimated Fair Value	164	298
Equal to or Greater than 12 Months Gross Unrealized Loss	22	4
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	6,781	14,447
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	404	911
Equal to or Greater than 12 Months Estimated Fair Value	6,112	5,251
Equal to or Greater than 12 Months Gross Unrealized Loss	864	913
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	2,136	3,530
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	75	166
Equal to or Greater than 12 Months Estimated Fair Value	851	429
Equal to or Greater than 12 Months Gross Unrealized Loss	64	55
RMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	5,692	13,467
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	127	287
Equal to or Greater than 12 Months Estimated Fair Value	3,259	2,431
Equal to or Greater than 12 Months Gross Unrealized Loss	190	196
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	321	1,618
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	55
Equal to or Greater than 12 Months Estimated Fair Value	79	168
Equal to or Greater than 12 Months Gross Unrealized Loss	10	22
ABS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	2,084	7,329
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	105	124
Equal to or Greater than 12 Months Estimated Fair Value	3,476	2,823
Equal to or Greater than 12 Months Gross Unrealized Loss	118	111
CMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	701	4,876
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	34	81
Equal to or Greater than 12 Months Estimated Fair Value	791	637
Equal to or Greater than 12 Months Gross Unrealized Loss	42	43
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	151	282
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	17	107
Equal to or Greater than 12 Months Estimated Fair Value	168	220
Equal to or Greater than 12 Months Gross Unrealized Loss	44	51
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	102	203
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	14	105
Equal to or Greater than 12 Months Estimated Fair Value	5	20
Equal to or Greater than 12 Months Gross Unrealized Loss	0	2
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	49	79
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	2
Equal to or Greater than 12 Months Estimated Fair Value	163	200
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 44	$ 49