Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ (250,057)	$ 64,556	$ (162,798)	$ 86,908	$ 126,312	$ 202,004	$ (34,791)	$ 122,839	$ (261,391)	$ 416,364	$ 383,520
Re-purchased Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)									0	851	0
Collars
Derivative [Line Items]
Derivative Fair Value Income (Loss)									(6,926)	16,539	42,836
Basis Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)									29,154	954	(26,800)
Puts
Derivative [Line Items]
Derivative Fair Value Income (Loss)									(18,201)	0	0
Calls
Derivative [Line Items]
Derivative Fair Value Income (Loss)									(18)	0	0
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)									(265,466)	398,020	367,484
Freight | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)									$ 66	$ 0	$ 0