Derivative Activities - Effects of Derivatives on Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Fair Value (Loss) Income	$ 18,491	$ 74,676	$ 195,245	$ (61,731)	$ 100,698	$ (34,591)	$ (103,290)	$ (14,009)	$ 226,681	$ (51,192)	$ 213,350
Swaptions
Derivative [Line Items]
Derivative Fair Value (Loss) Income									333	(6,556)	6,534
Collars
Derivative [Line Items]
Derivative Fair Value (Loss) Income									(3,903)	17,583	18,132
Basis Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income									6,661	(1,104)	(4,647)
Puts
Derivative [Line Items]
Derivative Fair Value (Loss) Income									0	0	10,929
Calls
Derivative [Line Items]
Derivative Fair Value (Loss) Income									(349)	(2,653)	987
Commodity | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income									219,968	(57,950)	181,095
Freight | Swaps
Derivative [Line Items]
Derivative Fair Value (Loss) Income									$ 3,971	$ (512)	$ 320