Derivative Instruments - Fair Value Amounts of Derivative Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	$ 58,048	$ 8,890
Gross Amounts Offset in the Balance Sheet (1)	(6,468)	(4,974)
Net Amounts of Assets Presented in the Balance Sheet	51,580	3,916
Gross Amounts of Recognized Liabilities	(7,069)	(10,056)
Gross Amounts Offset in the Balance Sheet (1)	6,468	4,974
Net Amounts of Liabilities Presented in the Balance Sheet	(601)	(5,082)
Derivative assets (current)
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	50,632	8,477
Gross Amounts Offset in the Balance Sheet (1)	(3,643)	(4,561)
Net Amounts of Assets Presented in the Balance Sheet	46,989	3,916
Derivative assets (noncurrent)
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	7,416	413
Gross Amounts Offset in the Balance Sheet (1)	(2,825)	(413)
Net Amounts of Assets Presented in the Balance Sheet	4,591	0
Accounts payable and accrued liabilities
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities	(3,643)	(8,972)
Gross Amounts Offset in the Balance Sheet (1)	3,643	4,561
Net Amounts of Liabilities Presented in the Balance Sheet	0	(4,411)
Other noncurrent liabilities
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities	(3,426)	(1,084)
Gross Amounts Offset in the Balance Sheet (1)	2,825	413
Net Amounts of Liabilities Presented in the Balance Sheet	$ (601)	$ (671)