v3.26.1
Financial Instruments (Narrative) (Details)
$ in Millions
6 Months Ended
Mar. 31, 2026
USD ($)
counterparty
Bcf
Derivative Instruments, Gain (Loss) [Line Items]  
After tax net hedging gains in accumulated other comprehensive income (loss) $ 80.3
After tax net hedging gains reclassified within twelve months 67.1
Fair market value of derivative liability with a credit-risk related contingency 0.2
Hedging Collateral Deposits 0.0
Foreign Currency Contracts  
Derivative Instruments, Gain (Loss) [Line Items]  
Hedging notional amount of forecasted transportation costs $ 38.5
Over the Counter Swaps, No Cost Collars and Foreign Currency Forward Contracts  
Derivative Instruments, Gain (Loss) [Line Items]  
Number of counterparties in which the company holds over-the-counter swap positions | counterparty 17
Number of counterparties in net gain position | counterparty 16
Credit risk exposure per counterparty $ 7.3
Maximum credit risk exposure per counterparty 14.3
Collateral received by the company $ 0.0
Cash Flow Hedges  
Derivative Instruments, Gain (Loss) [Line Items]  
Hedge duration 5 years
Cash Flow Hedges | Natural Gas Bcf  
Derivative Instruments, Gain (Loss) [Line Items]  
Nonmonetary notional amount of price risk cash flow hedge derivatives, natural gas | Bcf 374.1