Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments, Measured at Fair Value, Hedging Activities, and Concentrations of Credit Risk - Summary of Fair Value Measurements and Financial Statement Presentation (Detail)

v3.20.2
Financial Instruments, Measured at Fair Value, Hedging Activities, and Concentrations of Credit Risk - Summary of Fair Value Measurements and Financial Statement Presentation (Detail) - USD ($)
$ in Thousands
Sep. 30, 2020
Dec. 31, 2019
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets $ 20,934 $ 62
Short Term Investments [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets 20,802  
Commodity Derivative Contracts [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets 132 62
Level 1 [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets 20,934 62
Level 1 [Member] | Short Term Investments [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets 20,802  
Level 1 [Member] | Commodity Derivative Contracts [Member]    
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]    
Fair Values of Assets $ 132 $ 62