Loans, net and allowance for credit losses - Major Classification of Loans by Past Due Status (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Recorded Investment, Past Due.
Total Due	$ 2,818,043
Loans	2,818,043	$ 2,730,116
Loans > 90 Days and Accruing	59	748
Financial Assets, Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	4,631	3,986
30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	2,700	2,091
60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	1,152	367
Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due.
Total Due	779	1,528
Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	2,813,412	2,726,130
Commercial
Financing Receivable, Recorded Investment, Past Due.
Total Due	430,098
Loans	430,098	433,048
Commercial | Financial Assets, Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	170	261
Commercial | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	156	137
Commercial | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due		38
Commercial | Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due.
Total Due	14	86
Commercial | Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	429,928	432,787
Municipal
Financing Receivable, Recorded Investment, Past Due.
Total Due	169,278
Loans	169,278	166,210
Municipal | Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	169,278	166,210
Commercial real estate
Financing Receivable, Recorded Investment, Past Due.
Total Due	1,782,911
Loans	1,782,911	1,709,827
Commercial real estate | Financial Assets, Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	953	438
Commercial real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	92	102
Commercial real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	616	2
Commercial real estate | Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due.
Total Due	245	334
Commercial real estate | Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	1,781,958	1,709,389
Residential real estate
Financing Receivable, Recorded Investment, Past Due.
Total Due	342,459
Loans	342,459	330,728
Loans > 90 Days and Accruing	59	748
Residential real estate | Financial Assets, Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	2,876	2,278
Residential real estate | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	1,965	1,162
Residential real estate | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	444	128
Residential real estate | Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due.
Total Due	467	988
Residential real estate | Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	339,583	328,450
Consumer
Financing Receivable, Recorded Investment, Past Due.
Total Due	93,297
Loans	93,297	90,303
Consumer | Financial Assets, Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	632	1,009
Consumer | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	487	690
Consumer | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	92	199
Consumer | Greater than 90 Days
Financing Receivable, Recorded Investment, Past Due.
Total Due	53	120
Consumer | Financial Assets, Not Past Due
Financing Receivable, Recorded Investment, Past Due.
Total Due	$ 92,665	$ 89,294