Derivative instruments and hedging activities - Margin Balances (Details) - USD ($) $ in Thousands	Jul. 31, 2026	Jul. 31, 2025
Derivative instruments and hedging activities
Derivative Asset, Fair Value of Collateral	$ 8,749	$ 7,171
Derivative Liability, Fair Value of Collateral	3,760	2,442
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherAssetsNoncurrent
Derivative instruments and hedging activities
Derivative Asset, Fair Value of Collateral	311	949
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherLiabilitiesCurrent
Derivative instruments and hedging activities
Derivative Liability, Fair Value of Collateral	3,760	2,193
Location, Statement of Financial Position, Balance [Axis]: us-gaap:OtherLiabilitiesNoncurrent
Derivative instruments and hedging activities
Derivative Liability, Fair Value of Collateral		249
Location, Statement of Financial Position, Balance [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent
Derivative instruments and hedging activities
Derivative Asset, Fair Value of Collateral	$ 8,438	$ 6,222