Debt and Equity Transactions (Unaudited) Interests and Dividends (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Feb. 07, 2012
Class of Stock [Line Items]
Interest costs incurred	$ 56	$ 105	$ 210	$ 325
Interest costs capitalized	$ 14	$ 27	$ 62	$ 75
Annual Cash Dividend Before Increase					$ 1.00
Annual Cash Dividend Current					$ 1.25
Dividends Payable, Amount Per Share (in dollars per share)	$ 0.3125		$ 0.3125
Dividends Payable, Date Declared	Sep. 26, 2012
Dividends Payable, Date to be Paid	Nov. 01, 2012
Dividends Payable, Date of Record	Oct. 15, 2012