Investments in Qualified Affordable Housing Projects (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Investments in Qualified Affordable Housing Projects
Tax credits and other tax benefits	$ 3.8	$ 3.6	$ 11.5	$ 10.9
Investment Program, Proportional Amortization Method, Elected, Income Tax Credit and Other Income Tax Benefit, before Amortization, Statement of Income or Comprehensive Income [Extensible Enumeration]	Income Tax Expense (Benefit)	Income Tax Expense (Benefit)	Income Tax Expense (Benefit)	Income Tax Expense (Benefit)
Amortization	$ 3.6	$ 2.1	$ 10.5	$ 6.2
Investment Program, Proportional Amortization Method, Applied, Amortization Expense, Statement of Income or Comprehensive Income [Extensible Enumeration]	Income Tax Expense (Benefit)	Other Noninterest Expense	Income Tax Expense (Benefit)	Other Noninterest Expense
Carrying value	$ 81.6		$ 81.6		$ 101.8
Investment, Proportional Amortization Method, Elected, Statement of Financial Position [Extensible Enumeration]	Other Assets.		Other Assets.		Other Assets.
Funding obligation	$ 10.7		$ 10.7		$ 12.5
Percentage of remaining funding obligation expected to be funded	90.00%		90.00%