Loans, net and allowance for credit losses - Major Classifications of Loans Outstanding (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable
Loans	$ 2,818,043	$ 2,730,116
Loans	2,818,043
Commercial
Accounts, Notes, Loans and Financing Receivable
Loans	430,098	433,048
Loans	430,098
Municipal
Accounts, Notes, Loans and Financing Receivable
Loans	169,278	166,210
Loans	169,278
Commercial, Industrial and Municipal
Accounts, Notes, Loans and Financing Receivable
Loans		599,258
Loans	599,376
Real estate
Accounts, Notes, Loans and Financing Receivable
Loans		2,040,555
Loans	2,125,370
Commercial real estate
Accounts, Notes, Loans and Financing Receivable
Loans	1,782,911	1,709,827
Loans	1,782,911
Residential real estate
Accounts, Notes, Loans and Financing Receivable
Loans	342,459	330,728
Loans	342,459
Consumer
Accounts, Notes, Loans and Financing Receivable
Loans	93,297	90,303
Loans	93,297
Indirect Auto
Accounts, Notes, Loans and Financing Receivable
Loans		76,461
Loans	86,587
Consumer Other
Accounts, Notes, Loans and Financing Receivable
Loans		$ 13,842
Loans	$ 6,710