Premises and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment
Depreciation	$ 32.5	$ 38.8	$ 34.3
Premises and equipment, gross	651.1	673.1
Less accumulated depreciation	(244.5)	(245.9)
Premises and equipment, net	406.6	427.2
Land
Property, Plant and Equipment
Premises and equipment, gross	83.2	87.2
Buildings and improvements
Property, Plant and Equipment
Premises and equipment, gross	468.6	473.7
Furniture and equipment
Property, Plant and Equipment
Premises and equipment, gross	$ 99.3	$ 112.2