CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions		12 Months Ended
	Jan. 17, 2017	Dec. 31, 2016	Dec. 31, 2015
Natural gas and oil properties, using the full cost method, costs excluded from amortization		$ 2,105	$ 3,727
Common stock, par value		$ 0.01	$ 0.01
Common stock, shares authorized		1,250,000,000	1,250,000,000
Common stock, shares issued		495,248,369	390,138,549
Common stock, shares issued as stock dividend		7,166,389
Common stock, date dividend to be paid		Jan. 17, 2017
Common stock, date dividend declared		Dec. 12, 2016
Treasury stock, shares		31,269	47,149
Subsequent Event [Member]
Common stock, shares issued	2,751,410
Common stock, shares issued as stock dividend	2,751,410
Series B Preferred Stock [Member]
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	1,725,000
Preferred stock, shares outstanding		1,725,000	1,725,000