CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	20,000,000	20,000,000
Preferred stock, shares outstanding (shares)	7,225,713	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	684,560,678	664,795,509
Treasury stock, shares	1,384,506	1,437,724
Cash and cash equivalents ($1 and $1 attributable to our VIE)	$ 16	$ 825
VIE. proved natural gas and oil properties	64,305	63,843
VIE. accumulated depreciation, depletion and amortization	(60,506)	(59,365)
VIE. other current liabilities	1,544	2,219
Variable Interest Entities, Primary Beneficiary [Member]
Cash and cash equivalents ($1 and $1 attributable to our VIE)	1	1
VIE. proved natural gas and oil properties	488	488
VIE. accumulated depreciation, depletion and amortization	(445)	(428)
VIE. other current liabilities	$ 2	$ 8