Fair value measurements - Schedule of Notional Amounts and Fair Values of Derivatives by Product (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Derivatives, Fair Value [Line Items]
Notional derivative asset	$ 20,075	$ 9,900
Fair value derivative asset	98	34
Notional derivative liability	14,440,075	13,969,900
Fair value derivative liability	3,904	160
Futures | Commodity contracts
Derivatives, Fair Value [Line Items]
Notional derivative liability	14,420,000	13,960,000
Fair value derivative liability	3,812	133
TBAs | Other contracts
Derivatives, Fair Value [Line Items]
Notional derivative asset	20,075	9,900
Fair value derivative asset	98	34
Notional derivative liability	20,075	9,900
Fair value derivative liability	$ 92	$ 27