CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Preferred stock, par value (usd per share)	$ 0	$ 0.01
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares outstanding (shares)	7,251,515	7,251,515
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,000,000,000	1,000,000,000
Common Stock, Shares, Issued	666,468,000	660,888,000
Treasury stock, shares	2,147,724	1,552,533
Exact Value [Member]
Common Stock, Shares, Issued	666,467,664	660,888,159
Variable Interest Entities
Cash and cash equivalents attributable to our VIEs	$ 1	$ 1
Evaluated natural gas and oil properties attributable to our VIEs	488	498
Less:accumulated depreciation, depletion and amortization attributable to our VIEs	(58)	(6)
Short-term derivative liabilities attributable to our VIEs	4	9
Other current liabilities attributable to our VIEs	21	23
Long-term derivative liabilities attributable to our VIEs	$ 3	$ 10