Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 350,821	$ 332,964
Cost or Amortized Cost	2,914	2,997
Gross Unrealized OTTI Loss	(59)	(76)	$ (112)
Available-for-sale Securities, Debt Securities	387,508	351,402
Equity securities	3,333	3,321
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	350,821	332,964
Gross Unrealized Gain	40,062	23,883
Gross Unrealized Temporary Loss	3,316	5,369
Gross Unrealized OTTI Loss	59	76
Available-for-sale Securities, Debt Securities	387,508	351,402
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	95,218	96,466
Gross Unrealized Gain	10,302	6,583
Gross Unrealized Temporary Loss	905	2,255
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	104,615	100,794
U.S. government and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	59,591	56,499
Gross Unrealized Gain	10,167	5,373
Gross Unrealized Temporary Loss	21	226
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	69,737	61,646
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	56,813	56,003
Gross Unrealized Gain	3,865	3,019
Gross Unrealized Temporary Loss	1,466	1,822
Gross Unrealized OTTI Loss	0	2
Available-for-sale Securities, Debt Securities	59,212	57,198
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	52,293	45,451
Gross Unrealized Gain	10,113	5,269
Gross Unrealized Temporary Loss	145	221
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	62,261	50,499
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	43,223	37,914
Gross Unrealized Gain	1,790	1,366
Gross Unrealized Temporary Loss	364	424
Gross Unrealized OTTI Loss	51	59
Available-for-sale Securities, Debt Securities	44,598	38,797
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	14,403	13,723
Gross Unrealized Gain	3,024	1,795
Gross Unrealized Temporary Loss	11	67
Gross Unrealized OTTI Loss	6	10
Available-for-sale Securities, Debt Securities	17,410	15,441
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	16,689	14,498
Gross Unrealized Gain	141	131
Gross Unrealized Temporary Loss	309	229
Gross Unrealized OTTI Loss	3	6
Available-for-sale Securities, Debt Securities	16,518	14,394
CMBS (1)
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	12,591	12,410
Gross Unrealized Gain	660	347
Gross Unrealized Temporary Loss	95	125
Gross Unrealized OTTI Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	13,157	12,633
Equity securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,914	2,997
Gross Unrealized Gain	501	482
Gross Unrealized Temporary Loss	82	158
Gross Unrealized OTTI Loss	0	0
Equity securities	3,333	3,321
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,013	1,962
Gross Unrealized Gain	431	397
Gross Unrealized Temporary Loss	18	107
Gross Unrealized OTTI Loss	0	0
Equity securities	2,426	2,252
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	901	1,035
Gross Unrealized Gain	70	85
Gross Unrealized Temporary Loss	64	51
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 907	$ 1,069