v3.26.1
Derivatives and Hedging-Disclosures and Fair Value Measurements - Company's Commodity Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - Derivatives Not Designated as Hedging Instruments under FASB ASC 815-10 - Commodity Contract - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts $ 18,611 $ 8,316
Derivative Liabilities, commodity contracts (7,637) (8,822)
Fair asset value of derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts 17,892  
Derivative Liabilities, commodity contracts (7,073)  
Fair liability and fair asset value of derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts   7,561
Derivative Liabilities, commodity contracts   (8,169)
Deferred charges and other assets, net    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts 719 755
Derivative Liabilities, commodity contracts (564) (653)
Significant Other Observable Inputs Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts 18,611 8,316
Derivative Liabilities, commodity contracts (7,637) (8,822)
Significant Other Observable Inputs Level 2 | Fair asset value of derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts 17,892  
Derivative Liabilities, commodity contracts (7,073)  
Significant Other Observable Inputs Level 2 | Fair liability and fair asset value of derivative instruments    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts   7,561
Derivative Liabilities, commodity contracts   (8,169)
Significant Other Observable Inputs Level 2 | Deferred charges and other assets, net    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative Assets, commodity contracts 719 755
Derivative Liabilities, commodity contracts $ (564) $ (653)