Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 338,030	$ 330,354
Cost or Amortized Cost	2,983	2,744
Gross Unrealized OTTI Loss	37	8
Available-for-sale Securities, Debt Securities	364,084	350,889
Equity securities	3,415	3,194
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	28,876	25,420
Gross Unrealized Temporary Loss	2,859	4,893
Gross Unrealized OTTI Loss	(37)	(8)
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	94,759	94,558
Gross Unrealized Gain	8,426	7,351
Gross Unrealized Temporary Loss	586	1,056
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	102,599	100,853
U.S. government and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	54,356	53,326
Gross Unrealized Gain	5,922	4,977
Gross Unrealized Temporary Loss	399	780
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	59,879	57,523
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	54,708	50,923
Gross Unrealized Gain	6,712	6,600
Gross Unrealized Temporary Loss	312	385
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	61,108	57,138
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	57,709	55,676
Gross Unrealized Gain	3,819	3,132
Gross Unrealized Temporary Loss	1,054	1,752
Gross Unrealized OTTI Loss	0	(1)
Available-for-sale Securities, Debt Securities	60,474	57,057
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	37,355	36,293
Gross Unrealized Gain	1,472	1,244
Gross Unrealized Temporary Loss	334	554
Gross Unrealized OTTI Loss	(39)	(10)
Available-for-sale Securities, Debt Securities	38,532	36,993
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	14,234	14,566
Gross Unrealized Gain	2,060	1,733
Gross Unrealized Temporary Loss	40	122
Gross Unrealized OTTI Loss	0	1
Available-for-sale Securities, Debt Securities	16,254	16,176
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	14,088	13,920
Gross Unrealized Gain	124	101
Gross Unrealized Temporary Loss	74	141
Gross Unrealized OTTI Loss	3	3
Available-for-sale Securities, Debt Securities	14,135	13,877
CMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	10,821	11,092
Gross Unrealized Gain	341	282
Gross Unrealized Temporary Loss	60	103
Gross Unrealized OTTI Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	11,103	11,272
Equity securities
Available-for-sale Securities [Abstract]
Gross Unrealized Gain	463	513
Gross Unrealized Temporary Loss	31	63
Gross Unrealized OTTI Loss	0	0
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,280	1,927
Gross Unrealized Gain	411	488
Gross Unrealized Temporary Loss	16	14
Gross Unrealized OTTI Loss	0	0
Equity securities	2,675	2,401
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	703	817
Gross Unrealized Gain	52	25
Gross Unrealized Temporary Loss	15	49
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 740	$ 793