Borrowings and Borrowings Availability - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Short-term borrowings	$ 529,000,000	$ 220,900,000
Weighted average interest rate	5.25%	4.30%
FHLB Line of Credit
Debt Instrument [Line Items]
Line of credit, borrowing capacity	$ 1,300,000,000
Blanket lien, portion of real estate loan portfolio	2,300,000,000
Blanket lien, FHLB stock	21,700,000
Line of credit, outstanding	280,900,000	$ 221,800,000
Federal Funds Line of Credit
Debt Instrument [Line Items]
Line of credit, borrowing capacity	265,000,000
Line of credit, outstanding	0	0
FRB Line of Credit
Debt Instrument [Line Items]
Line of credit, borrowing capacity	294,100,000
Line of credit, outstanding	249,000,000	249,000,000
Federal Reserve Discount Window
Debt Instrument [Line Items]
Line of credit, borrowing capacity	561,600,000
Blanket lien, commercial and consumer loan portfolios	330,900,000
Blanket lien, securities	710,200,000
Line of credit, outstanding	$ 0	$ 0