Related party transactions - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Deposits from related parties	$ 245,084	$ 238,781
Lease expense			$ 5,019
Aviation Time Sharing Agreement
Related Party Transaction [Line Items]
Payments to related party	161	266	208
Certain Executive Officers, Certain Management and Directors and Their Associates \| Unfunded Loan Commitment
Related Party Transaction [Line Items]
Unfunded commitments	23,059	19,404
Director
Related Party Transaction [Line Items]
Unamortized leasehold improvements	53	86
Operating lease expense	$ 510	$ 509
Lease expense			$ 516

Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

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Amount of operating lease expense. Excludes sublease income.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

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Amount of transactions with related party during the financial reporting period.

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