Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative [Line Items]
Derivative Fair Value (Loss) Income	$ (61,731)	$ (14,009)
Swaptions
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(3,291)	3,599
Collars
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(4,524)	(77)
Calls
Derivative [Line Items]
Derivative Fair Value (Loss) Income	0	177
Basis Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	3,415	(864)
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	(57,418)	(16,536)
Freight | Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income	$ 87	$ (308)