Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 286,684	$ 271,701
Cost or Amortized Cost	2,386	2,464
Gross Unrealized OTTI Loss	37	8
Available-for-sale Securities, Debt Securities	308,894	289,563
Equity securities	2,776	2,894
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	24,276	21,801
Gross Unrealized Temporary Loss	2,103	3,946
Gross Unrealized OTTI Loss	(37)	(7)
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	75,221	73,280
Gross Unrealized Gain	6,827	6,027
Gross Unrealized Temporary Loss	393	764
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	81,655	78,543
U.S. government and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	43,911	41,294
Gross Unrealized Gain	4,056	3,682
Gross Unrealized Temporary Loss	303	543
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	47,664	44,433
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	54,618	49,864
Gross Unrealized Gain	6,486	6,485
Gross Unrealized Temporary Loss	315	373
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	60,789	55,976
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	52,185	49,333
Gross Unrealized Gain	3,705	2,901
Gross Unrealized Temporary Loss	750	1,572
Gross Unrealized OTTI Loss	0	(1)
Available-for-sale Securities, Debt Securities	55,140	50,663
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	30,368	28,393
Gross Unrealized Gain	1,222	1,039
Gross Unrealized Temporary Loss	232	410
Gross Unrealized OTTI Loss	(40)	(10)
Available-for-sale Securities, Debt Securities	31,398	29,032
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	10,754	10,977
Gross Unrealized Gain	1,615	1,340
Gross Unrealized Temporary Loss	24	85
Gross Unrealized OTTI Loss	0	1
Available-for-sale Securities, Debt Securities	12,345	12,231
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	11,702	11,266
Gross Unrealized Gain	114	90
Gross Unrealized Temporary Loss	42	128
Gross Unrealized OTTI Loss	3	3
Available-for-sale Securities, Debt Securities	11,771	11,225
CMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	7,925	7,294
Gross Unrealized Gain	251	237
Gross Unrealized Temporary Loss	44	71
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	8,132	7,460
Equity Securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	415	483
Gross Unrealized Temporary Loss	25	53
Gross Unrealized OTTI Loss	0	0
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,883	1,827
Gross Unrealized Gain	379	464
Gross Unrealized Temporary Loss	20	13
Gross Unrealized OTTI Loss	0	0
Equity securities	2,242	2,278
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	503	637
Gross Unrealized Gain	36	19
Gross Unrealized Temporary Loss	5	40
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 534	$ 616