Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ 165,557	$ 86,908
Collars
Derivative [Line Items]
Derivative Fair Value Income (Loss)	9,475	0
Puts
Derivative [Line Items]
Derivative Fair Value Income (Loss)	6,707	0
Calls
Derivative [Line Items]
Derivative Fair Value Income (Loss)	510	0
Basis Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	(17,972)	7,275
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	166,752	79,644
Freight | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ 85	$ (11)