Borrowings - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Secured lines of credit	$ 4,500,000
FHLB borrowings	$ 50,000	$ 150,000
Average interest rate on Federal Home Loan Bank borrowings	3.64%
Weighted average interest rate on balances outstanding	3.23%
Subordinated Debt
Debt Instrument [Line Items]
Debt	$ 25,000	$ 12,300
Interest rate	3.375%	5.50%
Fair value adjustment	$ (3,900)	$ 400
Subordinated Debt | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate	2.03%	5.33%
Federal Reserve Bank Advances
Debt Instrument [Line Items]
Secured lines of credit	$ 2,800,000
Federal Home Loan Bank Advances
Debt Instrument [Line Items]
Secured lines of credit	1,700,000
Trust I & II
Debt Instrument [Line Items]
Junior subordinated deferrable interest notes issued	41,200
SBCF Statutory Trust III
Debt Instrument [Line Items]
Junior subordinated deferrable interest notes issued	$ 12,400
SBCF Statutory Trust III | Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate	5.38%