Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 329,203	$ 334,780
Cost or Amortized Cost	3,096	3,076
Gross Unrealized OTTI Loss	99	112	$ 218
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	351,578	365,425
Equity securities	3,399	3,631
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	329,203	334,780
Gross Unrealized Gain	26,749	32,634
Gross Unrealized Temporary Loss	4,275	1,877
Gross Unrealized OTTI Loss	99	112
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	351,578	365,425
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	95,156	96,235
Gross Unrealized Gain	7,525	10,343
Gross Unrealized Temporary Loss	1,717	624
Gross Unrealized OTTI Loss	7	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	100,957	105,954
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	56,545	57,695
Gross Unrealized Gain	3,465	4,651
Gross Unrealized Temporary Loss	1,606	664
Gross Unrealized OTTI Loss	0	7
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	58,404	61,675
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	45,346	47,327
Gross Unrealized Gain	5,361	5,500
Gross Unrealized Temporary Loss	184	161
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	50,523	52,666
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	38,696	38,064
Gross Unrealized Gain	1,720	2,102
Gross Unrealized Temporary Loss	288	214
Gross Unrealized OTTI Loss	78	106
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	40,050	39,846
U.S. Treasury and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	53,624	54,654
Gross Unrealized Gain	6,216	6,892
Gross Unrealized Temporary Loss	169	30
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	59,671	61,516
CMBS (1)
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	12,001	13,762
Gross Unrealized Gain	437	615
Gross Unrealized Temporary Loss	77	46
Gross Unrealized OTTI Loss	(1)	(1)
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	12,362	14,332
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	14,157	14,121
Gross Unrealized Gain	162	240
Gross Unrealized Temporary Loss	181	112
Gross Unrealized OTTI Loss	6	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	14,132	14,249
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	13,678	12,922
Gross Unrealized Gain	1,863	2,291
Gross Unrealized Temporary Loss	53	26
Gross Unrealized OTTI Loss	9	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $329,203 and $334,780, respectively; includes $4,293 and $4,266, respectively, relating to variable interest entities)	15,479	15,187
Equity securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	3,096	3,076
Gross Unrealized Gain	450	622
Gross Unrealized Temporary Loss	147	67
Gross Unrealized OTTI Loss	0	0
Equity securities	3,399	3,631
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,040	1,990
Gross Unrealized Gain	375	554
Gross Unrealized Temporary Loss	99	28
Gross Unrealized OTTI Loss	0	0
Equity securities	2,316	2,516
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,056	1,086
Gross Unrealized Gain	75	68
Gross Unrealized Temporary Loss	48	39
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 1,083	$ 1,115