Employee Benefit Plans Pension and Postretirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
New percentage of eligible earnings used to determine retirement benefits (in hundredths)	5.00%
Recognized pension expense	$ 30		$ 27		$ 31
Non Qualified Pension Plan Expense	1		1		1
Components of net periodic costs [Abstract]
Interest cost on accumulated benefit obligation	16		16		16
Expected return on plan assets	(7)		(9)		(9)
Amortization of transition obligation	6		6		6
Amortization of loss	3		1		0
Benefit enhancement	1		1		0
Net postretirement benefit cost	19		15		13
Assumptions used to determine net periodic benefit (income) cost [Abstract]
Discount rate (in hundredths)	4.80%		5.20%		5.70%
Expected return on plan assets (in hundredths)	6.00%		7.50%		7.50%
Change in Benefit Obligation [Roll Forward]
Accumulated benefit obligation, beginning of year	335		306
Interest cost	16		16
Benefits paid	(21)		(23)
Participant contributions	2		2
Medicare drug reimbursement	2		3
Actuarial loss	17		31
Accumulated benefit obligation, end of year	351		335		306
Change in Plan Assets [Roll Forward]
Plan assets, beginning of year	116	[1]	122
Benefits paid	(21)		(23)
Employer contributions	9		9
Participant contributions	2		2
Actual investment return	9		6
Plan assets, end of year	115	[1]	116	[1]	122
Amounts Recognized in Balance Sheets [Abstract]
Net liability, end of year	(236)		(219)
Actuarial Assumptions [Abstract]
Discount Rate (in hundredths)	3.90%		4.80%
Expected long-term return on assets (in hundredths)	6.00%		6.00%
Assumed Health Care Cost Trend Rates [Abstract]
Healthcare cost trend rate assumed for the next year (in hundredths)	9.00%		8.00%
Prescription drug cost trend rate assumed for the next year (in hundredths)	9.00%		8.00%
Rate to which the cost trend rate is assumed to decline (ultimate trend rate) (in hundredths)	5.50%		5.50%
Year that the healthcare rate reaches the ultimate trend rate	2017		2017
Year that the prescription drug rate reaches the ultimate trend rate	2017		2017
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Support, Methodology and Source Data	one-half to ninety-nine years
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Effect of One Percentage Point Increase on Postretirement Benefit Obligation	13
Effect of One Percentage Point Decrease on Postretirement Benefit Obligation	(11)
Effect of One Percentage Point Increase on Total Service and Interest Cost	0
Effect of One Percentage Point Decrease on Total Service and Interest Cost	0
Domestic equity securities [Member]
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	13.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	23.00%
International equity securities [Member]
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	3.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	13.00%
Fixed Income [Member]
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	68.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	78.00%
Cash and Cash Equivalents [Member]
Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Target Plan Asset Allocations Range Minimum	0.00%
Defined Benefit Plan, Target Plan Asset Allocations Range Maximum	2.00%
Pension Plans, Defined Benefit [Member]
Amounts Recognized in Balance Sheets [Abstract]
Other liabilities-benefit obligations	$ (236)		$ (219)

[1] 74% of the amount invested in mutual funds is in fixed income securities; 18% is in U.S. equities and 8% is in international equities.