Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Derivative Fair Value (Loss) Income	$ (88,426)	$ 64,556	$ 188,326	$ (11,334)
Swaptions
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(7,602)		(7,602)
Collars
Derivative [Line Items]
Derivative Fair Value (Loss) Income	956	1,320	15,221	1,320
Puts
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(73)	2,842	9,646	2,842
Calls
Derivative [Line Items]
Derivative Fair Value (Loss) Income	104		1,144
Basis Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	6,113	21,853	(2,554)	24,929
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(87,861)	38,662	172,457	(40,270)
Freight | Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	$ (63)	$ (121)	$ 14	$ (155)