Defined Contribution and Defined Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Contribution and Defined Benefit Plans [Abstract]
Defined Contribution Plan, Cost Recognized	$ 11	$ 10	$ 9
Employer Matching Contribution Percentage	100.00%
Deferral Election Percentage For Employer Matching Contribution	5.00%
Employee Deferral Limit Percentage	75.00%
Pension and Other Postretirement Defined Benefit Plans, Liabilities From Acquisition			6
Grandfathered Pension Liability Employees			130
Defined Benefit Plan, Assets for Plan Benefits	12	10
Pension and Other Postretirement Defined Benefit Plans, Liabilities	21	18
Defined Benefit Plan, Amounts Recognized in Balance Sheet	9	8
Defined Benefit Plan, Net Periodic Benefit Cost	1	1	9
Defined Benefit Plan, Net Periodic Benefit Cost Related To Voluntary Retirement Incentive			8
Number Of Employees That Accepted The Voluntray Retirement Incentive			31
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax	1	3
Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year	2	3
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	1
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 1