Investments (Continuous Gross Unrealized Losses for Fixed Maturity and Equity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 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	1,076	327
Total number of securities in an unrealized loss position equal to or greater than 12 months	302	420
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	$ 9,053	$ 1,967
Less than 12 Months Gross Unrealized Loss	453	36
Equal to or Greater than 12 Months Estimated Fair Value	1,308	2,027
Equal to or Greater than 12 Months Gross Unrealized Loss	162	239
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	2,665	784
Less than 12 Months Gross Unrealized Loss	159	16
Equal to or Greater than 12 Months Estimated Fair Value	456	621
Equal to or Greater than 12 Months Gross Unrealized Loss	56	66
U.S. Treasury and agency 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	2,520	200
Less than 12 Months Gross Unrealized Loss	153	0
Equal to or Greater than 12 Months Estimated Fair Value	0	0
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
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	1,494	494
Less than 12 Months Gross Unrealized Loss	58	8
Equal to or Greater than 12 Months Estimated Fair Value	136	203
Equal to or Greater than 12 Months Gross Unrealized Loss	10	18
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	1,141	62
Less than 12 Months Gross Unrealized Loss	32	6
Equal to or Greater than 12 Months Estimated Fair Value	469	781
Equal to or Greater than 12 Months Gross Unrealized Loss	72	108
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	495	208
Less than 12 Months Gross Unrealized Loss	2	1
Equal to or Greater than 12 Months Estimated Fair Value	153	266
Equal to or Greater than 12 Months Gross Unrealized Loss	9	17
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	407	44
Less than 12 Months Gross Unrealized Loss	30	2
Equal to or Greater than 12 Months Estimated Fair Value	57	55
Equal to or Greater than 12 Months Gross Unrealized Loss	15	25
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	149	59
Less than 12 Months Gross Unrealized Loss	4	1
Equal to or Greater than 12 Months Estimated Fair Value	37	101
Equal to or Greater than 12 Months Gross Unrealized Loss	0	5
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	182	116
Less than 12 Months Gross Unrealized Loss	15	2
Equal to or Greater than 12 Months Estimated Fair Value	0	0
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
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	105	10
Less than 12 Months Gross Unrealized Loss	21	1
Equal to or Greater than 12 Months Estimated Fair Value	41	57
Equal to or Greater than 12 Months Gross Unrealized Loss	9	22
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	2	10
Less than 12 Months Gross Unrealized Loss	3	1
Equal to or Greater than 12 Months Estimated Fair Value	7	7
Equal to or Greater than 12 Months Gross Unrealized Loss	0	0
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	103	0
Less than 12 Months Gross Unrealized Loss	18	0
Equal to or Greater than 12 Months Estimated Fair Value	34	50
Equal to or Greater than 12 Months Gross Unrealized Loss	$ 9	$ 22