Available-For-Sale Securities (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Investments, Debt and Equity Securities [Abstract]
Pretax charges recognized for "other-than-temporary" declines in the market values of equities securities	$ 0	$ 4	$ 1	$ 4
Less than 12 months
Fair Value	96		96		164
Unrealized Losses	3		3		8
12 months or more
Fair Value	52		52		53
Unrealized Losses	6		6		10
Total
Fair Value	148		148		217
Unrealized Losses	9		9		18
Corporate bonds
Less than 12 months
Fair Value					54
Unrealized Losses					1
12 months or more
Fair Value					1
Unrealized Losses					0
Total
Fair Value					55
Unrealized Losses					1
Asset-backed Securities
Less than 12 months
Fair Value	0		0		1
Unrealized Losses	0		0		0
12 months or more
Fair Value	20		20		20
Unrealized Losses	3		3		5
Total
Fair Value	20		20		21
Unrealized Losses	3		3		5
U.S. governmental agency mortgage-backed securities
Less than 12 months
Fair Value	74		74		51
Unrealized Losses	1		1		1
12 months or more
Fair Value	4		4		0
Unrealized Losses	0		0		0
Total
Fair Value	78		78		51
Unrealized Losses	1		1		1
Residential
Less than 12 months
Fair Value	0		0		3
Unrealized Losses	0		0		0
12 months or more
Fair Value	15		15		18
Unrealized Losses	1		1		3
Total
Fair Value	15		15		21
Unrealized Losses	1		1		3
Commercial
Less than 12 months
Fair Value					15
Unrealized Losses					0
12 months or more
Fair Value					8
Unrealized Losses					1
Total
Fair Value					23
Unrealized Losses					1
Large capitalization value
Less than 12 months
Fair Value	22		22		36
Unrealized Losses	2		2		5
12 months or more
Fair Value	13		13		6
Unrealized Losses	2		2		1
Total
Fair Value	35		35		42
Unrealized Losses	4		4		6
Smaller company growth
Less than 12 months
Fair Value					4
Unrealized Losses					1
12 months or more
Fair Value					0
Unrealized Losses					0
Total
Fair Value					4
Unrealized Losses					$ 1