Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 333,985	$ 330,354
Cost or Amortized Cost	2,919	2,744
Gross Unrealized OTTI Loss	19	8
Available-for-sale Securities, Debt Securities	355,528	350,889
Equity securities	3,377	3,194
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	25,777	25,420
Gross Unrealized Temporary Loss	4,253	4,893
Gross Unrealized OTTI Loss	(19)	(8)
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	94,491	94,558
Gross Unrealized Gain	7,337	7,351
Gross Unrealized Temporary Loss	915	1,056
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	100,913	100,853
U.S. government and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	52,486	53,326
Gross Unrealized Gain	5,058	4,977
Gross Unrealized Temporary Loss	664	780
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	56,880	57,523
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	54,169	50,923
Gross Unrealized Gain	6,649	6,600
Gross Unrealized Temporary Loss	380	385
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	60,438	57,138
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	56,664	55,676
Gross Unrealized Gain	3,304	3,132
Gross Unrealized Temporary Loss	1,503	1,752
Gross Unrealized OTTI Loss	0	(1)
Available-for-sale Securities, Debt Securities	58,465	57,057
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	36,785	36,293
Gross Unrealized Gain	1,280	1,244
Gross Unrealized Temporary Loss	484	554
Gross Unrealized OTTI Loss	(23)	(10)
Available-for-sale Securities, Debt Securities	37,604	36,993
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	14,555	14,566
Gross Unrealized Gain	1,768	1,733
Gross Unrealized Temporary Loss	96	122
Gross Unrealized OTTI Loss	2	1
Available-for-sale Securities, Debt Securities	16,225	16,176
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	13,819	13,920
Gross Unrealized Gain	105	101
Gross Unrealized Temporary Loss	112	141
Gross Unrealized OTTI Loss	3	3
Available-for-sale Securities, Debt Securities	13,809	13,877
CMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	11,016	11,092
Gross Unrealized Gain	276	282
Gross Unrealized Temporary Loss	99	103
Gross Unrealized OTTI Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	11,194	11,272
Equity securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	492	513
Gross Unrealized Temporary Loss	34	63
Gross Unrealized OTTI Loss	0	0
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,174	1,927
Gross Unrealized Gain	449	488
Gross Unrealized Temporary Loss	11	14
Gross Unrealized OTTI Loss	0	0
Equity securities	2,612	2,401
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	745	817
Gross Unrealized Gain	43	25
Gross Unrealized Temporary Loss	23	49
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 765	$ 793