Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ 111,195	$ (162,798)	$ 276,752	$ (75,890)
Collars
Derivative [Line Items]
Derivative Fair Value Income (Loss)	4,790		14,265
Puts
Derivative [Line Items]
Derivative Fair Value Income (Loss)	3,012		9,719
Calls
Derivative [Line Items]
Derivative Fair Value Income (Loss)	529		1,040
Basis Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	9,304	(4,199)	(8,668)	3,075
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	93,567	(158,576)	260,319	(78,931)
Freight | Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ (7)	$ (23)	$ 77	$ (34)