Loans and Allowance for Credit Losses for Loans - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non covered loans net of unearned discount and deferred loan fees	$ 15,100		$ 15,100		$ 45,300
Accrued interest	207,800		207,800		208,900
Transfer of loans to loans held for sale, net	3,900	$ 10,200	14,137	$ 823,091		$ 10,000
Sales of loans	10,200
Allowance for credit loss, write-off	541	$ 638			1,200	$ 4,200
Proceeds from sale of commercial premium finance lending division			0	$ 98,060
Other real estate owned	$ 4,800		$ 4,800		$ 12,200
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Accrued interest receivable		Accrued interest receivable		Accrued interest receivable
In formal foreclosure proceedings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage and consumer loans secured by residential real estate properties	$ 2,900		$ 2,900		$ 4,600