Fair value measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 13,746	$ 17,050
Derivatives asset, Fair Value	154	1,762
Derivative liability, Notional	7,633,746	1,914,275
Derivative liability, Fair Value	2,020	1,805
TBAs | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	8,746	1,775
Derivatives asset, Fair Value	153	1,762
Derivative liability, Notional	8,746	1,775
Derivative liability, Fair Value	146	1,761
Futures | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	5,000
Derivatives asset, Fair Value	1
Futures | Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative liability, Notional	7,625,000	1,912,500
Derivative liability, Fair Value	$ 1,874	44
Forward repurchase agreements | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional		15,000
Derivatives asset, Fair Value		0
Other | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional		275
Derivatives asset, Fair Value		$ 0