Investments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Available-for-sale Securities [Abstract]
Amortized Cost	$ 344,791	$ 329,811
Cost or Amortized Cost	2,838	3,208
Gross Unrealized OTTI Loss	441	724	601
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	378,005	350,271
Equity securities	2,803	3,023
Fixed maturity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	344,791	329,811
Gross Unrealized Gain	35,455	25,973
Gross Unrealized Temporary Loss	1,800	4,789
Gross Unrealized OTTI Loss	441	724
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	378,005	350,271
% of Total	100.00%	100.00%
U.S. corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	102,483	98,621
Gross Unrealized Gain	11,975	8,544
Gross Unrealized Temporary Loss	516	1,380
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	113,942	105,785
% of Total	30.10%	30.20%
Foreign corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	60,235	61,568
Gross Unrealized Gain	5,400	3,789
Gross Unrealized Temporary Loss	379	1,338
Gross Unrealized OTTI Loss	(1)	1
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	65,257	64,018
% of Total	17.30%	18.30%
Foreign government debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	52,205	49,840
Gross Unrealized Gain	5,323	3,053
Gross Unrealized Temporary Loss	123	357
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	57,405	52,536
% of Total	15.20%	15.00%
RMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	38,788	42,092
Gross Unrealized Gain	2,685	2,281
Gross Unrealized Temporary Loss	454	1,033
Gross Unrealized OTTI Loss	428	703
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	40,591	42,637
% of Total	10.70%	12.20%
U.S. Treasury and agency securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	44,964	34,132
Gross Unrealized Gain	6,489	5,882
Gross Unrealized Temporary Loss	5	2
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	51,448	40,012
% of Total	13.60%	11.40%
CMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	18,495	18,565
Gross Unrealized Gain	1,029	730
Gross Unrealized Temporary Loss	84	218
Gross Unrealized OTTI Loss	0	8
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	19,440	19,069
% of Total	5.10%	5.40%
ABS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	14,809	13,018
Gross Unrealized Gain	370	278
Gross Unrealized Temporary Loss	160	305
Gross Unrealized OTTI Loss	14	12
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	15,005	12,979
% of Total	4.00%	3.70%
State and political subdivision securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	12,812	11,975
Gross Unrealized Gain	2,184	1,416
Gross Unrealized Temporary Loss	79	156
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $344,791 and $329,811, respectively; includes $3,349 and $3,225, respectively, relating to variable interest entities)	14,917	13,235
% of Total	4.00%	3.80%
Equity Securities [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,838	3,208
Gross Unrealized Gain	164	114
Gross Unrealized Temporary Loss	199	299
Gross Unrealized OTTI Loss	0	0
Equity securities	2,803	3,023
% of Total	100.00%	100.00%
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,999	2,219
Gross Unrealized Gain	112	83
Gross Unrealized Temporary Loss	42	97
Gross Unrealized OTTI Loss	0	0
Equity securities	2,069	2,205
% of Total	73.80%	72.90%
Non-redeemable preferred stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	839	989
Gross Unrealized Gain	52	31
Gross Unrealized Temporary Loss	157	202
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 734	$ 818
% of Total	26.20%	27.10%