v3.26.1
Financial Instruments - Narrative (Details)
3 Months Ended 9 Months Ended
Jun. 30, 2026
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
MMcf
Jun. 30, 2025
USD ($)
Sep. 30, 2025
USD ($)
Derivative [Line Items]          
Purchase commitment volume | MMcf     18,662    
Contract netting $ 0   $ 0   $ 0
Cash collateral 0   0   $ 0
Net (gain) loss on settled interest rate agreements (6,100,000) $ (5,100,000) (18,400,000) $ (15,400,000)  
Net realized gains in AOCI $ 460,400,000   $ 460,400,000    
Designated As Hedge | Gas Purchases | Commodity contracts          
Derivative [Line Items]          
Purchase commitment volume | MMcf     23,800    
Designated As Hedge | Gas Purchases | Commodity contracts | Minimum          
Derivative [Line Items]          
Hedging percent 25.00%   25.00%    
Designated As Hedge | Gas Purchases | Commodity contracts | Maximum          
Derivative [Line Items]          
Hedging percent 50.00%   50.00%