CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016		Jun. 30, 2016		Dec. 31, 2015
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 3,382		$ 3,382		$ 3,727
Common stock, par value	$ 0.01		$ 0.01		$ 0.01
Common stock, shares authorized	1,250,000,000		1,250,000,000		1,250,000,000
Common stock, shares issued	392,496,825	[1]	392,496,825	[1]	390,138,549
Common stock, shares declared as stock dividend	2,100,119
Treasury stock, shares	31,269		31,269		47,149
Series B Preferred Stock [Member]
Preferred stock, par value	$ 0.01		$ 0.01		$ 0.01
Preferred stock, shares authorized	10,000,000		10,000,000		10,000,000
Preferred stock, dividend rate			6.25%		6.25%
Liquidation preference per share	$ 1,000		$ 1,000		$ 1,000
Preferred stock, shares issued	1,725,000		1,725,000		1,725,000
Preferred stock, shares outstanding	1,725,000		1,725,000		1,725,000

[1] (1) Does not include 98,900,000 shares of common stock issued in July 2016.