Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ 74,676	$ (34,591)	$ 208,190	$ (151,890)
Swaptions
Derivative [Line Items]
Derivative Fair Value Income (Loss)	10,358	7,093	39,451	4,100
Collars
Derivative [Line Items]
Derivative Fair Value Income (Loss)	356	(3,965)	(3,590)	(4,031)
Calls
Derivative [Line Items]
Derivative Fair Value Income (Loss)	(224)	197	(224)	526
Basis Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	3,448	(2,350)	7,801	(9,043)
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	60,090	(35,868)	161,799	(143,598)
Freight | Swaps
Derivative [Line Items]
Derivative Fair Value Income (Loss)	$ 648	$ 302	$ 2,953	$ 156