Mortgage Servicing Rights - Schedule of Mortgage Servicing Rights (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Servicing Asset at Amortized Value, Balance [Roll Forward]
Balance at end of year, net of valuation reserve	$ 23.1	$ 25.7
Mortgage loans
Servicing Asset at Amortized Value, Balance [Roll Forward]
Servicing asset at amortized cost, before valuation reserve, beginning	25.7	28.3	$ 31.1
Originations of mortgage servicing rights	0.5	0.7	1.1
Amortization expense	(3.1)	(3.3)	(3.9)
Servicing asset at amortized cost, before valuation reserve, ending	23.1	25.7	28.3
Less valuation reserve	0.0
Principal balance of serviced loans underlying mortgage servicing rights	$ 2,591.3	$ 2,853.2	$ 3,091.1
Mortgage servicing rights as a percentage of serviced loans	0.0089	0.0090	0.0092