CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
CONSOLIDATED BALANCE SHEETS [Abstract]
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 1,767	$ 1,817
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,250,000,000	1,250,000,000
Common stock, shares issued	586,174,491	512,134,311
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, dividend rate	6.25%	6.25%
Liquidation preference per share	$ 1,000	$ 1,000
Preferred stock, shares issued		1,725,000
Preferred stock, shares outstanding		1,725,000
Treasury stock, shares	4,860,280	31,269