Long-Term Debt and Other Borrowed Funds - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Long-Term Debt and Lease Obligation	$ 370.8	$ 120.8
Advance from Federal Home Loan Bank		2,603.0
Other Short-term Borrowings	$ 2,342.0	2,603.0
Parent
Fixed-to-floating rate (percent)	5.25%
Long-Term Debt	$ 99.1	$ 99.0
Notes Payable to FHLB \| Subsidiaries \| Federal Home Loan Bank Advances
Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds	4,416.7
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	$ 6,008.7
5.01% fixed rate borrowings in tenors up to one-month
Fixed-to-floating rate (percent)	5.03%	5.52%
Capital Lease Obligation, 8.00% \| Subsidiaries \| Capital Lease Obligations
Fixed-to-floating rate (percent)	8.00%
Finance Lease, Liability	$ 0.8	$ 0.9
Note Payable, maturing December 31, 2041, 1.00% \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	1.00%
Long-Term Debt	$ 5.1	5.1
Note Payable maturing March 31, 2038, 1.30% \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	1.30%
Long-Term Debt	$ 2.0	2.0
Note Payable maturing June 1, 2034, 1.30% \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	1.30%
Long-Term Debt	$ 0.6	0.6
Note Payable maturing December 31, 2045, 1.12% \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	1.12%
Long-Term Debt	$ 6.8	6.8
Note Payable maturing December 31, 2046, 1.35% \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	1.35%
Long-Term Debt	$ 6.4	6.4
FHLB Borrowing maturing July 2025 \| Subsidiaries \| Notes Payable, Other Payables
Fixed-to-floating rate (percent)	4.72%
Long-Term Debt	$ 250.0	$ 0.0

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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