Loans, net and allowance for credit losses - Allocation of Allowance for Loan Losses and Related Loans by Major Classification of Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Allowance for loan losses:
Ending balance: individually evaluated for impairment	$ 14	$ 40
Ending balance: collectively evaluated for impairment	25,430	27,432
Loans receivable:
Ending balance	2,818,043	2,730,116
Ending balance: individually evaluated for impairment	1,666	3,921
Ending balance: collectively evaluated for impairment	2,816,363	2,726,195
Commercial
Allowance for loan losses:
Ending balance: individually evaluated for impairment	14	19
Ending balance: collectively evaluated for impairment	2,467	4,346
Loans receivable:
Ending balance	430,098	433,048
Ending balance: individually evaluated for impairment	10	98
Ending balance: collectively evaluated for impairment	430,074	432,950
Municipal
Allowance for loan losses:
Ending balance: collectively evaluated for impairment	2,318	1,247
Loans receivable:
Ending balance	169,278	166,210
Ending balance: collectively evaluated for impairment	169,278	166,210
Commercial real estate
Allowance for loan losses:
Ending balance: collectively evaluated for impairment	15,692	17,915
Loans receivable:
Ending balance	1,782,911	1,709,827
Ending balance: individually evaluated for impairment	867	2,063
Ending balance: collectively evaluated for impairment	1,782,044	1,707,764
Residential real estate
Allowance for loan losses:
Ending balance: individually evaluated for impairment		21
Ending balance: collectively evaluated for impairment	3,868	3,051
Loans receivable:
Ending balance	342,459	330,728
Ending balance: individually evaluated for impairment	789	1,760
Ending balance: collectively evaluated for impairment	341,670	328,968
Consumer
Allowance for loan losses:
Ending balance: collectively evaluated for impairment	1,085	873
Loans receivable:
Ending balance	93,297	90,303
Ending balance: collectively evaluated for impairment	$ 93,297	$ 90,303

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
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-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

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The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

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