Fair value measurements - Notional Amounts and Fair Values of Derivatives by Product (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	$ 5,525	$ 17,050
Derivatives asset, Fair Value	4,734	1,762
Derivative liability, Notional	8,226,525	1,914,275
Derivative liability, Fair Value	7,753	1,805
TBAs | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional	5,525	1,775
Derivatives asset, Fair Value	4,734	1,762
Derivative liability, Notional	5,525	1,775
Derivative liability, Fair Value	4,696	1,761
Futures | Commodity contracts
Derivatives, Fair Value [Line Items]
Derivative liability, Notional	8,117,000	1,912,500
Derivative liability, Fair Value	3,057	44
Forward repurchase agreements | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional		15,000
Derivatives asset, Fair Value		0
Derivative liability, Notional	104,000
Derivative liability, Fair Value	$ 0
Other Security | Other contracts
Derivatives, Fair Value [Line Items]
Derivatives asset, Notional		275
Derivatives asset, Fair Value		$ 0