Condensed Consolidated Statements Of Cash Flows (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Consolidated Statements Of Cash Flows [Abstract]
Dividends payable on common and preferred stock	$ 99	$ 90
Natural gas and oil properties adjusted as a result of an increase in accrued exploration and development costs	26	22
Other property and equipment adjusted as a result of an increase in accrued costs	24	5
Liabilities related to the purchase of proved and unproved properties	$ 79	$ 202