Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	$ 292,257	$ 286,069
Gross Unrealized OTTI Loss	34	41
Debt Securities, Available-for-sale	306,331	308,931
Equity securities	$ 1,483	$ 2,513
Percentage of Available-for-sale Equity Securities	100.00%	100.00%
Fixed Maturity Securities
Debt Securities, Available-for-sale [Abstract]
Gross Unrealized Gain	$ 18,872	$ 24,765
Gross Unrealized Temporary Loss	4,832	1,945
Gross Unrealized OTTI Loss	(34)	(42)
U.S. corporate
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	81,382	76,005
Gross Unrealized Gain	4,233	7,007
Gross Unrealized Temporary Loss	1,589	351
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	84,026	82,661
U.S. government and agency
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	42,701	43,446
Gross Unrealized Gain	3,229	4,227
Gross Unrealized Temporary Loss	543	279
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	45,387	47,394
Foreign government
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	56,106	55,351
Gross Unrealized Gain	6,082	6,495
Gross Unrealized Temporary Loss	506	312
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	61,682	61,534
Foreign corporate
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	52,930	52,409
Gross Unrealized Gain	2,780	3,836
Gross Unrealized Temporary Loss	1,433	676
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	54,277	55,569
RMBS
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	27,390	27,846
Gross Unrealized Gain	976	1,145
Gross Unrealized Temporary Loss	556	233
Gross Unrealized OTTI Loss	(35)	(42)
Debt Securities, Available-for-sale	27,845	28,800
State and political subdivision
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	10,683	10,752
Gross Unrealized Gain	1,395	1,717
Gross Unrealized Temporary Loss	52	13
Gross Unrealized OTTI Loss	0	1
Debt Securities, Available-for-sale	12,026	12,455
ABS
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	12,818	12,213
Gross Unrealized Gain	85	116
Gross Unrealized Temporary Loss	36	39
Gross Unrealized OTTI Loss	1	(1)
Debt Securities, Available-for-sale	12,866	12,291
CMBS
Debt Securities, Available-for-sale [Abstract]
Cost or Amortized Cost	8,247	8,047
Gross Unrealized Gain	92	222
Gross Unrealized Temporary Loss	117	42
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	8,222	8,227
Equity Securities
Debt Securities, Available-for-sale [Abstract]
Equity securities	1,483	2,513
Common Stock
Debt Securities, Available-for-sale [Abstract]
Equity securities	$ 1,062	$ 2,035
Percentage of Available-for-sale Equity Securities	71.60%	81.00%
Non-redeemable preferred stock
Debt Securities, Available-for-sale [Abstract]
Equity securities	$ 421	$ 478
Percentage of Available-for-sale Equity Securities	28.40%	19.00%