Investments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Available-for-sale Securities [Abstract]
Amortized Cost	$ 338,871	$ 329,811
Cost or Amortized Cost	2,973	3,208
Gross Unrealized OTTI Loss	679	724	601
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	366,339	350,271
Equity securities	2,882	3,023
Fixed maturity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	338,871	329,811
Gross Unrealized Gain	30,950	25,973
Gross Unrealized Temporary Loss	2,803	4,789
Gross Unrealized OTTI Loss	679	724
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	366,339	350,271
% of Total	100.00%	100.00%
U.S. corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	101,275	98,621
Gross Unrealized Gain	9,941	8,544
Gross Unrealized Temporary Loss	843	1,380
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	110,373	105,785
% of Total	30.10%	30.20%
Foreign corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	59,878	61,568
Gross Unrealized Gain	4,116	3,789
Gross Unrealized Temporary Loss	648	1,338
Gross Unrealized OTTI Loss	1	1
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	63,345	64,018
% of Total	17.30%	18.30%
Foreign government debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	51,582	49,840
Gross Unrealized Gain	4,780	3,053
Gross Unrealized Temporary Loss	169	357
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	56,193	52,536
% of Total	15.30%	15.00%
RMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	40,077	42,092
Gross Unrealized Gain	2,378	2,281
Gross Unrealized Temporary Loss	726	1,033
Gross Unrealized OTTI Loss	665	703
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	41,064	42,637
% of Total	11.20%	12.20%
U.S. Treasury and agency securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	41,217	34,132
Gross Unrealized Gain	6,629	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: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	47,841	40,012
% of Total	13.10%	11.40%
CMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	18,270	18,565
Gross Unrealized Gain	850	730
Gross Unrealized Temporary Loss	103	218
Gross Unrealized OTTI Loss	0	8
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	19,017	19,069
% of Total	5.20%	5.40%
ABS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	13,828	13,018
Gross Unrealized Gain	294	278
Gross Unrealized Temporary Loss	217	305
Gross Unrealized OTTI Loss	13	12
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	13,892	12,979
% of Total	3.80%	3.70%
State and political subdivision securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	12,744	11,975
Gross Unrealized Gain	1,962	1,416
Gross Unrealized Temporary Loss	92	156
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $338,871 and $329,811, respectively; includes $3,289 and $3,225, respectively, relating to variable interest entities)	14,614	13,235
% of Total	4.00%	3.80%
Equity Securities [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,973	3,208
Gross Unrealized Gain	130	114
Gross Unrealized Temporary Loss	221	299
Gross Unrealized OTTI Loss	0	0
Equity securities	2,882	3,023
% of Total	100.00%	100.00%
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,060	2,219
Gross Unrealized Gain	95	83
Gross Unrealized Temporary Loss	61	97
Gross Unrealized OTTI Loss	0	0
Equity securities	2,094	2,205
% of Total	72.70%	72.90%
Non-redeemable preferred stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	913	989
Gross Unrealized Gain	35	31
Gross Unrealized Temporary Loss	160	202
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 788	$ 818
% of Total	27.30%	27.10%