Investment securities - Amortized Cost and Fair Value of Investment Securities Aggregated by Investment Category (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Investment Securities
Available-for-sale, Amortized Cost	$ 569,885	$ 519,112
Available-for-sale, Gross Unrealized Gains	743	5,294
Available-for-sale, Gross Unrealized Losses	35,146	7,085
Available-for-sale, Fair Value	535,482	517,321
Held-to-maturity, Amortized Cost	95,829	71,213
Held-to-maturity, Gross Unrealized Gains	31	129
Held-to-maturity, Gross Unrealized Losses	6,580	896
Held-to-maturity, Fair value	89,280	70,446
U.S. Treasury securities
Investment Securities
Available-for-sale, Amortized Cost	250,268	193,849
Available-for-sale, Gross Unrealized Gains	28	107
Available-for-sale, Gross Unrealized Losses	12,624	2,382
Available-for-sale, Fair Value	237,672	191,574
U.S. Government-sponsored enterprises state and municipals
Investment Securities
Available-for-sale, Amortized Cost	28,174	33,435
Available-for-sale, Gross Unrealized Gains	31	343
Available-for-sale, Gross Unrealized Losses	184
Available-for-sale, Fair Value	28,021	33,778
Mortgage-backed Securities, U.S. Government agencies
Investment Securities
Available-for-sale, Amortized Cost	1,563	1,790
Available-for-sale, Gross Unrealized Gains	9	53
Available-for-sale, Gross Unrealized Losses	1
Available-for-sale, Fair Value	1,571	1,843
Held-to-maturity, Amortized Cost	18,511	18,802
Held-to-maturity, Gross Unrealized Losses	1,315	392
Held-to-maturity, Fair value	17,196	18,410
Mortgage-backed Securities, U.S. Government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	105,652	109,018
Available-for-sale, Gross Unrealized Gains	50	939
Available-for-sale, Gross Unrealized Losses	9,168	2,925
Available-for-sale, Fair Value	96,534	107,032
Held-to-maturity, Amortized Cost	66,052	40,935
Held-to-maturity, Gross Unrealized Gains	1	3
Held-to-maturity, Gross Unrealized Losses	4,612	448
Held-to-maturity, Fair value	61,441	40,490
Commercial mortgage-backed Securities, U.S. government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	12,396	12,542
Available-for-sale, Gross Unrealized Gains	14	406
Available-for-sale, Gross Unrealized Losses	129
Available-for-sale, Fair Value	12,281	12,948
Corporate Debt Securities
Investment Securities
Available-for-sale, Amortized Cost	3,000	3,000
Available-for-sale, Gross Unrealized Losses	176	82
Available-for-sale, Fair Value	2,824	2,918
State and Municipals, Taxable
Investment Securities
Available-for-sale, Amortized Cost	69,027	69,066
Available-for-sale, Gross Unrealized Gains	106	994
Available-for-sale, Gross Unrealized Losses	6,021	1,082
Available-for-sale, Fair Value	63,112	68,978
State and Municipals, Tax-exempt
Investment Securities
Available-for-sale, Amortized Cost	99,805	96,412
Available-for-sale, Gross Unrealized Gains	505	2,452
Available-for-sale, Gross Unrealized Losses	6,843	614
Available-for-sale, Fair Value	93,467	98,250
Held-to-maturity, Amortized Cost	11,266	11,476
Held-to-maturity, Gross Unrealized Gains	30	126
Held-to-maturity, Gross Unrealized Losses	653	56
Held-to-maturity, Fair value	$ 10,643	$ 11,546

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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