Investments (Fair Values And Unrealized Losses By Investment Category And By The Duration Of The Securities' Continuous Unrealized Loss Position) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 223	$ 729
Less than 12 months Unrealized Losses	12	48
12 months or more Fair Value	17	88
12 months or more Unrealized Losses	1	5
Total Fair Value	240	817
Total Unrealized Losses	13	53
Fixed Maturities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	112	391
Less than 12 months Unrealized Losses	2	13
12 months or more Fair Value	17	69
12 months or more Unrealized Losses	1	5	4
Total Fair Value	129	460
Total Unrealized Losses	3	18
Fixed Maturities [Member] | States, Municipalities And Political Subdivisions [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	53
Less than 12 months Unrealized Losses	1
12 months or more Fair Value		12
Total Fair Value	53	12
Total Unrealized Losses	1
Fixed Maturities [Member] | United States Government [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value		1
Total Fair Value		1
Fixed Maturities [Member] | Government-Sponsored Enterprises [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	1	10
Total Fair Value	1	10
Fixed Maturities [Member] | Corporate Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	58	380
Less than 12 months Unrealized Losses	1	13
12 months or more Fair Value	17	57
12 months or more Unrealized Losses	1	5
Total Fair Value	75	437
Total Unrealized Losses	2	18
Equity Securities [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	111	338
Less than 12 months Unrealized Losses	10	35
12 months or more Fair Value		19
12 months or more Unrealized Losses			1
Total Fair Value	111	357
Total Unrealized Losses	10	35
Equity Securities [Member] | Common Stock [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	107	333
Less than 12 months Unrealized Losses	9	35
Total Fair Value	107	333
Total Unrealized Losses	9	35
Equity Securities [Member] | Preferred Stock [Member]
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	4	5
Less than 12 months Unrealized Losses	1
12 months or more Fair Value		19
Total Fair Value	4	24
Total Unrealized Losses	$ 1