Retirement Benefits (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Defined Contribution Pension [Member]	Dec. 31, 2011 Defined Contribution Pension [Member]	Dec. 31, 2010 Defined Contribution Pension [Member]	Dec. 31, 2012 Employee Retirement Savings Plan [Member]	Dec. 31, 2011 Employee Retirement Savings Plan [Member]	Dec. 31, 2010 Employee Retirement Savings Plan [Member]	Aug. 01, 2008 Defined Benefit Postretirement Life Insurance [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Defined Benefit Plan, Market Related Value Assumption, Term	5 years
Defined Benefit Plan, Settlements, Plan Assets	$ 1,200,000,000
Defined Contribution Plan, Cost Recognized		167,000,000	131,000,000	123,000,000	70,000,000	54,000,000	52,000,000
Deferred Compensation Arrangement with Individual, Recorded Liability								$ 25,000