Fair value measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Derivatives, Fair Value [Line Items]
Derivative asset, Notional	$ 9,900	$ 360
Derivatives asset, Fair Value	34	0
Derivative liability, notional	13,969,900	11,475,360
Derivative liability, Fair Value	160	1,071
Commodity contracts | Futures
Derivatives, Fair Value [Line Items]
Derivative liability, notional	13,960,000	11,475,000
Derivative liability, Fair Value	133	1,071
Other contracts | TBAs
Derivatives, Fair Value [Line Items]
Derivative asset, Notional	9,900	360
Derivatives asset, Fair Value	34	0
Derivative liability, notional	9,900	360
Derivative liability, Fair Value	$ 27	$ 0