Indebtedness (Credit Facilities) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding	$ 0
Line of Credit Facility, Maximum Borrowing Capacity	8,000,000,000
364-day revolving credit, expiring February 11, 2014 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date	Feb. 12, 2013
Line of Credit Facility, Maximum Borrowing Capacity	2,000,000,000
Multi-year revolving credit, expiring March 31, 2015 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	2,500,000,000
Multi-year revolving credit, expiring October 25, 2016 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,500,000,000