Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale Securities [Abstract]
Amortized Cost	$ 328,833	$ 334,780
Cost or Amortized Cost	3,117	3,076
Gross Unrealized OTTI Loss	50	112	$ 218
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	351,353	365,425
Equity securities	3,677	3,631
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Amortized Cost	328,833	334,780
Gross Unrealized Gain	26,029	32,634
Gross Unrealized Temporary Loss	3,459	1,877
Gross Unrealized OTTI Loss	50	112
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	351,353	365,425
U.S. corporate
Available-for-sale Securities [Abstract]
Amortized Cost	94,375	96,235
Gross Unrealized Gain	7,977	10,343
Gross Unrealized Temporary Loss	1,206	624
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	101,146	105,954
Foreign corporate
Available-for-sale Securities [Abstract]
Amortized Cost	56,284	57,695
Gross Unrealized Gain	3,882	4,651
Gross Unrealized Temporary Loss	1,068	664
Gross Unrealized OTTI Loss	0	7
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	59,098	61,675
Foreign government
Available-for-sale Securities [Abstract]
Amortized Cost	46,004	47,327
Gross Unrealized Gain	5,206	5,500
Gross Unrealized Temporary Loss	153	161
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	51,057	52,666
RMBS
Available-for-sale Securities [Abstract]
Amortized Cost	40,188	38,064
Gross Unrealized Gain	1,719	2,102
Gross Unrealized Temporary Loss	345	214
Gross Unrealized OTTI Loss	44	106
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	41,518	39,846
U.S. Treasury and agency
Available-for-sale Securities [Abstract]
Amortized Cost	53,083	54,654
Gross Unrealized Gain	4,854	6,892
Gross Unrealized Temporary Loss	399	30
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	57,538	61,516
CMBS (1)
Available-for-sale Securities [Abstract]
Amortized Cost	11,472	13,762
Gross Unrealized Gain	453	615
Gross Unrealized Temporary Loss	84	46
Gross Unrealized OTTI Loss	(1)	(1)
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	11,842	14,332
ABS
Available-for-sale Securities [Abstract]
Amortized Cost	13,897	14,121
Gross Unrealized Gain	203	240
Gross Unrealized Temporary Loss	103	112
Gross Unrealized OTTI Loss	7	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	13,990	14,249
State and political subdivision
Available-for-sale Securities [Abstract]
Amortized Cost	13,530	12,922
Gross Unrealized Gain	1,735	2,291
Gross Unrealized Temporary Loss	101	26
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $328,833 and $334,780, respectively; includes $4,335 and $4,266, respectively, relating to variable interest entities)	15,164	15,187
Equity securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	3,117	3,076
Gross Unrealized Gain	633	622
Gross Unrealized Temporary Loss	73	67
Gross Unrealized OTTI Loss	0	0
Equity securities	3,677	3,631
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,058	1,990
Gross Unrealized Gain	558	554
Gross Unrealized Temporary Loss	27	28
Gross Unrealized OTTI Loss	0	0
Equity securities	2,589	2,516
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,059	1,086
Gross Unrealized Gain	75	68
Gross Unrealized Temporary Loss	46	39
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 1,088	$ 1,115