Premises and equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disclosure Of Premises And Equipmen Additional Information [Abstract]
Depreciation, Depletion and Amortization	$ 57.1	$ 58.5	$ 55.1
Occupancy Expense	26.4	26.5	24.8
Equipment technology and software and other operating expenses	30.7	32.0	30.3
Rental Income	$ 11.5	$ 13.1	$ 13.1