Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Available-for-sale Securities [Abstract]
Amortized Cost	$ 330,900	$ 340,870
Cost or Amortized Cost	2,978	2,838
Gross Unrealized OTTI Loss	241	361	724
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	348,787	374,266
Equity securities	3,241	2,891
Fixed maturity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	330,900	340,870
Gross Unrealized Gain	22,071	35,144
Gross Unrealized Temporary Loss	3,943	1,387
Gross Unrealized OTTI Loss	241	361
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	348,787	374,266
U.S. corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	101,107	102,669
Gross Unrealized Gain	7,650	11,887
Gross Unrealized Temporary Loss	1,266	430
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	107,491	114,126
Foreign corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	60,374	61,806
Gross Unrealized Gain	3,871	5,654
Gross Unrealized Temporary Loss	597	277
Gross Unrealized OTTI Loss	0	(1)
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	63,648	67,184
Foreign government debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	49,400	51,967
Gross Unrealized Gain	3,969	5,440
Gross Unrealized Temporary Loss	365	71
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	53,004	57,336
RMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	34,412	35,666
Gross Unrealized Gain	1,698	2,477
Gross Unrealized Temporary Loss	403	315
Gross Unrealized OTTI Loss	229	349
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	35,478	37,479
U.S. Treasury and agency securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	41,926	41,874
Gross Unrealized Gain	2,967	6,104
Gross Unrealized Temporary Loss	739	11
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	44,154	47,967
CMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	16,425	18,177
Gross Unrealized Gain	635	1,009
Gross Unrealized Temporary Loss	164	57
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	16,896	19,129
ABS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	14,023	15,762
Gross Unrealized Gain	296	404
Gross Unrealized Temporary Loss	146	156
Gross Unrealized OTTI Loss	12	13
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	14,161	15,997
State and political subdivision securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	13,233	12,949
Gross Unrealized Gain	985	2,169
Gross Unrealized Temporary Loss	263	70
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $330,900 and $340,870, respectively; includes $3,940 and $3,378, respectively, relating to variable interest entities)	13,955	15,048
Equity Securities [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,978	2,838
Gross Unrealized Gain	396	212
Gross Unrealized Temporary Loss	133	159
Gross Unrealized OTTI Loss	0	0
Equity securities	3,241	2,891
Common Stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,948	2,034
Gross Unrealized Gain	336	147
Gross Unrealized Temporary Loss	14	19
Gross Unrealized OTTI Loss	0	0
Equity securities	2,270	2,162
Non-redeemable preferred stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,030	804
Gross Unrealized Gain	60	65
Gross Unrealized Temporary Loss	119	140
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 971	$ 729