Loans and Allowance for Credit Losses Activity in the Allowance for Credit Losses (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 287,442,000	$ 248,564,000	$ 269,366,000	$ 249,001,000	$ 249,001,000
Loans charged off	(7,279,000)	(3,724,000)	(28,969,000)	(7,242,000)
Recoveries of loans previously charged off	2,181,000	3,272,000	7,896,000	11,593,000
Net loans (charged off) recovered	(5,098,000)	(452,000)	(21,073,000)	4,351,000
Provision for credit losses	10,395,000	9,637,000	44,446,000	4,397,000
Ending balance	292,739,000	266,838,000	292,739,000	266,838,000	$ 269,366,000
Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	(458,000)	1,367,000	(218,000)	1,157,000
Off-Balance-Sheet, Credit Loss, Liability	16,110,000	16,074,000	16,110,000	16,074,000
Loans - Excluding OBS Credit Exposure
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses at acquisition		1,135,000		1,135,000
Loans charged off	(7,279,000)	(3,724,000)	(28,969,000)	(7,242,000)
Recoveries of loans previously charged off	2,181,000	3,272,000	7,896,000	11,593,000
Net loans (charged off) recovered	(5,098,000)	(452,000)	(21,073,000)	4,351,000
Provision for credit losses	10,395,000	9,637,000	44,446,000	4,397,000
Loans - Excluding OBS Credit Exposure | Real estate - commercial mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses at acquisition		1,051,000		1,051,000
Loans charged off	(860,000)	(86,000)	(14,452,000)	(238,000)
Recoveries of loans previously charged off	101,000	29,000	916,000	3,677,000
Net loans (charged off) recovered	(759,000)	(57,000)	(13,536,000)	3,439,000
Provision for credit losses	$ 2,403,000	$ 11,144,000	$ 18,026,000	$ (7,717,000)