Borrowings - Short-term Borrowings (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Federal Reserve Bank Borrowings
Short-Term Debt [Line Items]
Pledged collateral	$ 6.4	$ 6.4
Federal Home Loan Bank Advances
Short-Term Debt [Line Items]
Pledged collateral	754.0	754.0
Repurchase agreements
Short-Term Debt [Line Items]
Borrowings	0.0	2.6
Federal Reserve Bank Borrowings
Short-Term Debt [Line Items]
Available borrowing capacity	3,500.0	3,500.0
Federal Home Loan Bank Advances
Short-Term Debt [Line Items]
Available borrowing capacity	$ 605.5	$ 605.5

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant