Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Available-for-sale Securities [Abstract]
Amortized Cost	$ 335,626	$ 340,870
Cost or Amortized Cost	2,922	2,838
Gross Unrealized OTTI Loss	277	361	724
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	356,514	374,266
Equity securities	3,231	2,891
Fixed maturity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	335,626	340,870
Gross Unrealized Gain	24,560	35,144
Gross Unrealized Temporary Loss	3,395	1,387
Gross Unrealized OTTI Loss	277	361
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	356,514	374,266
U.S. corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	101,627	102,669
Gross Unrealized Gain	8,398	11,887
Gross Unrealized Temporary Loss	1,017	430
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	109,008	114,126
Foreign corporate securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	60,928	61,806
Gross Unrealized Gain	3,893	5,654
Gross Unrealized Temporary Loss	636	277
Gross Unrealized OTTI Loss	(1)	(1)
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	64,186	67,184
Foreign government debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	48,199	51,967
Gross Unrealized Gain	4,373	5,440
Gross Unrealized Temporary Loss	275	71
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	52,297	57,336
RMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	35,295	35,666
Gross Unrealized Gain	1,848	2,477
Gross Unrealized Temporary Loss	436	315
Gross Unrealized OTTI Loss	266	349
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	36,441	37,479
U.S. Treasury and agency securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	44,254	41,874
Gross Unrealized Gain	3,683	6,104
Gross Unrealized Temporary Loss	511	11
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	47,426	47,967
CMBS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	16,680	18,177
Gross Unrealized Gain	757	1,009
Gross Unrealized Temporary Loss	174	57
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	17,263	19,129
ABS [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	15,502	15,762
Gross Unrealized Gain	332	404
Gross Unrealized Temporary Loss	167	156
Gross Unrealized OTTI Loss	12	13
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	15,655	15,997
State and political subdivision securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	13,141	12,949
Gross Unrealized Gain	1,276	2,169
Gross Unrealized Temporary Loss	179	70
Gross Unrealized OTTI Loss	0	0
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $335,626 and $340,870, respectively; includes $4,064 and $3,378, respectively, relating to variable interest entities)	14,238	15,048
Equity Securities [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,922	2,838
Gross Unrealized Gain	403	212
Gross Unrealized Temporary Loss	94	159
Gross Unrealized OTTI Loss	0	0
Equity securities	3,231	2,891
Common Stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,895	2,034
Gross Unrealized Gain	344	147
Gross Unrealized Temporary Loss	8	19
Gross Unrealized OTTI Loss	0	0
Equity securities	2,231	2,162
Non-redeemable preferred stock [Member]
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	1,027	804
Gross Unrealized Gain	59	65
Gross Unrealized Temporary Loss	86	140
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 1,000	$ 729