Derivative and Hedging Activities Interest Income and Interest Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Disclosure Interest Income And Interest Expense [Abstract]
Interest Expense on Senior Notes	$ 186	$ 174
Interest Expense on Credit Facilities	12	21
Interest Expense on Term Loans	29	0
(Gains) losses on interest rate derivatives	4	4
Amortization of Financing Costs and Discounts	19	1
Capitalized Interest	(229)	(188)
Interest Expense	$ 21	$ 12