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		Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross Amount		$ 34,595	$ 6,870
Netting Adjustments	[1]	(3,764)	(845)
Net Amount Presented in Balance Sheets		30,831	6,025
Gross Amount		(7,478)	(1,171)
Netting Adjustments	[1]	3,764	845
Net Amount Presented in Balance Sheets		(3,714)	(326)
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		33,762	4,960
Netting Adjustments	[1]	(3,719)	(845)
Net Amount Presented in Balance Sheets		30,043	4,115
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		833	1,910
Netting Adjustments	[1]	(45)
Net Amount Presented in Balance Sheets		788	1,910
Current Liabilities [Member] | Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		(5,081)	(845)
Netting Adjustments	[1]	3,719	845
Net Amount Presented in Balance Sheets		(1,362)
Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross Amount		(2,397)	(326)
Netting Adjustments	[1]	45
Net Amount Presented in Balance Sheets		$ (2,352)	$ (326)

[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.