Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) $ in Millions	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
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	3,981	5,321
Total number of securities in an unrealized loss position equal to or greater than 12 months	1,544	1,790
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	$ 60,818	$ 68,339
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,428	2,924
Equal to or Greater than 12 Months Estimated Fair Value	15,194	17,103
Equal to or Greater than 12 Months Gross Unrealized Loss	1,394	1,961
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	10,077	16,147
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	310	656
Equal to or Greater than 12 Months Estimated Fair Value	3,305	3,684
Equal to or Greater than 12 Months Gross Unrealized Loss	276	400
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	20,004	13,500
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	378	760
Equal to or Greater than 12 Months Estimated Fair Value	189	141
Equal to or Greater than 12 Months Gross Unrealized Loss	21	20
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	6,448	6,228
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	227	271
Equal to or Greater than 12 Months Estimated Fair Value	1,012	924
Equal to or Greater than 12 Months Gross Unrealized Loss	85	114
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	7,081	11,613
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	234	639
Equal to or Greater than 12 Months Estimated Fair Value	6,741	6,127
Equal to or Greater than 12 Months Gross Unrealized Loss	820	1,112
RMBS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	12,033	12,943
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	215	403
Equal to or Greater than 12 Months Estimated Fair Value	1,753	2,618
Equal to or Greater than 12 Months Gross Unrealized Loss	80	141
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	1,062	2,636
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	32	114
Equal to or Greater than 12 Months Estimated Fair Value	97	85
Equal to or Greater than 12 Months Gross Unrealized Loss	8	9
ABS
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	2,711	2,702
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	10	33
Equal to or Greater than 12 Months Estimated Fair Value	1,496	2,789
Equal to or Greater than 12 Months Gross Unrealized Loss	67	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	1,402	2,570
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	22	48
Equal to or Greater than 12 Months Estimated Fair Value	601	735
Equal to or Greater than 12 Months Gross Unrealized Loss	37	54
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	359	301
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	16	23
Equal to or Greater than 12 Months Estimated Fair Value	136	176
Equal to or Greater than 12 Months Gross Unrealized Loss	15	40
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	331	105
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	16	14
Equal to or Greater than 12 Months Estimated Fair Value	2	11
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	28	196
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	9
Equal to or Greater than 12 Months Estimated Fair Value	134	165
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 15	$ 40