Investments in Qualified Affordable Housing Projects (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Investments in Qualified Affordable Housing Projects
Tax credits and other tax benefits	$ 3.8	$ 3.6	$ 7.7	$ 7.2
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	$ 3.5	$ 2.1	$ 6.9	$ 4.1
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	$ 85.0		$ 85.0		$ 101.8
Investment, Proportional Amortization Method, Elected, Statement of Financial Position [Extensible Enumeration]	Other Assets.		Other Assets.		Other Assets.
Funding obligation	$ 11.3		$ 11.3		$ 12.5
Percentage of remaining funding obligation expected to be funded	91.00%		91.00%