Derivative Instruments - Fair Value of Derivative Instruments on a Gross basis and on a Net Basis as Presented in Consolidated Balance Sheets (Detail) - Commodity Contract [Member] - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross Amount		$ 62,015	$ 34,595
Netting Adjustments	[1]	(6,867)	(3,764)
Net Amount Presented in Balance Sheets		55,148	30,831
Gross Amount		(15,572)	(7,478)
Netting Adjustments	[1]	6,867	3,764
Net Amount Presented in Balance Sheets		(8,705)	(3,714)
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		61,763	33,762
Netting Adjustments	[1]	(6,718)	(3,719)
Net Amount Presented in Balance Sheets		55,045	30,043
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		252	833
Netting Adjustments	[1]	(149)	(45)
Net Amount Presented in Balance Sheets		103	788
Current Liabilities [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		(7,229)	(5,081)
Netting Adjustments	[1]	6,718	3,719
Net Amount Presented in Balance Sheets		(511)	(1,362)
Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		(8,343)	(2,397)
Netting Adjustments	[1]	149	45
Net Amount Presented in Balance Sheets		$ (8,194)	$ (2,352)

[1] The Company has agreements in place that allow for the financial right to offset for derivative assets and derivative liabilities at settlement or in the event of a default under the agreements.