Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Total number of securities in an unrealized loss position less than 12 months	2,188	1,941
Total number of securities in an unrealized loss position equal to or greater than 12 months	1,070	1,335
Fixed maturity securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	20,430	13,721
Less than 12 Months Gross Unrealized Loss	486	293
Equal to or Greater than 12 Months Estimated Fair Value	10,163	13,447
Equal to or Greater than 12 Months Gross Unrealized Loss	1,079	1,455
U.S. corporate securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	5,868	3,799
Less than 12 Months Gross Unrealized Loss	171	88
Equal to or Greater than 12 Months Estimated Fair Value	2,663	3,695
Equal to or Greater than 12 Months Gross Unrealized Loss	273	342
Foreign corporate securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	4,884	2,783
Less than 12 Months Gross Unrealized Loss	146	96
Equal to or Greater than 12 Months Estimated Fair Value	2,144	2,873
Equal to or Greater than 12 Months Gross Unrealized Loss	157	180
Foreign government debt securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,428	1,431
Less than 12 Months Gross Unrealized Loss	28	22
Equal to or Greater than 12 Months Estimated Fair Value	462	543
Equal to or Greater than 12 Months Gross Unrealized Loss	40	49
RMBS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,284	735
Less than 12 Months Gross Unrealized Loss	42	31
Equal to or Greater than 12 Months Estimated Fair Value	3,235	4,098
Equal to or Greater than 12 Months Gross Unrealized Loss	405	633
U.S. Treasury, agency and government guaranteed securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	2,645	1,951
Less than 12 Months Gross Unrealized Loss	30	11
Equal to or Greater than 12 Months Estimated Fair Value	0	0
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
CMBS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	1,440	842
Less than 12 Months Gross Unrealized Loss	16	11
Equal to or Greater than 12 Months Estimated Fair Value	401	577
Equal to or Greater than 12 Months Gross Unrealized Loss	37	46
ABS [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	2,356	1,920
Less than 12 Months Gross Unrealized Loss	43	30
Equal to or Greater than 12 Months Estimated Fair Value	1,015	1,410
Equal to or Greater than 12 Months Gross Unrealized Loss	107	139
State and political subdivision securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	525	260
Less than 12 Months Gross Unrealized Loss	10	4
Equal to or Greater than 12 Months Estimated Fair Value	243	251
Equal to or Greater than 12 Months Gross Unrealized Loss	60	66
Equity Securities [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	123	201
Less than 12 Months Gross Unrealized Loss	8	18
Equal to or Greater than 12 Months Estimated Fair Value	286	309
Equal to or Greater than 12 Months Gross Unrealized Loss	78	141
Common Stock [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	67	201
Less than 12 Months Gross Unrealized Loss	7	18
Equal to or Greater than 12 Months Estimated Fair Value	12	14
Equal to or Greater than 12 Months Gross Unrealized Loss	1	1
Non-redeemable preferred stock [Member]
Continuous Gross Unrealized Loss and OTTI Loss for Fixed Maturity and Equity Securities Available-for-Sale
Less than 12 months Estimated Fair Value	56	0
Less than 12 Months Gross Unrealized Loss	1	0
Equal to or Greater than 12 Months Estimated Fair Value	274	295
Equal to or Greater than 12 Months Gross Unrealized Loss	77	140