Loans and Allowance for Credit Losses for Loans - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Feb. 29, 2024	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non covered loans net of unearned discount and deferred loan fees		$ 48,100,000			$ 48,100,000		$ 85,400,000
Accrued interest		221,300,000			221,300,000		222,200,000
Transfer of loans to loans held for sale, net		823,100,000			823,091,000	$ 10,000,000	10,000,000.0
Proceeds from sale of commercial premium finance lending division					98,060,000	0
Loans held for investment, current					20,900,000
Sales of loans		0		$ 0	0	$ 0
Other real estate owned		$ 7,200,000			$ 7,200,000		$ 0
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]		Accrued interest receivable			Accrued interest receivable		Accrued interest receivable
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Commercial Premium Finance Lending Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of commercial premium finance lending division	$ 96,800,000
Disposal group, discontinued operation, assets	95,500,000
Sale of loans held for investment, loan amount	93,600,000
Disposal group, including discontinued operation, liabilities	$ 2,800,000
Gain (loss) on disposition of business			$ 3,600,000
Commercial Real Estate | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, sale			151,000,000
Transfer of loans to loans held for sale, net		$ 823,100,000
Commercial Real Estate | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, sale			45,600,000
Transfer of loans to loans held for sale, net			$ 34,100,000
Residential real estate properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other real estate owned		0			$ 0		$ 0
In formal foreclosure proceedings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage and consumer loans secured by residential real estate properties		$ 4,200,000			$ 4,200,000		$ 1,600,000