CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Statement of Cash Flows [Abstract]
Dividends payable on common and preferred stock	$ 99	$ 99
Natural gas and oil properties adjusted as a result of an increase in accrued acquisition, drilling and completion costs	(103)	148
Other property and equipment adjusted as a result of an increase in accrued costs	57	90
Liabilities related to the purchase of proved and unproved properties	$ 60	$ 173