Investment securities - Amortized Cost and Fair Value of Investment Securities Aggregated by Investment Category (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investment Securities
Available-for-sale, Amortized Cost	$ 519,112	$ 286,215
Available-for-sale, Gross Unrealized Gains	5,294	9,899
Available-for-sale, Gross Unrealized Losses	7,085	203
Available-for-sale, Fair Value	517,321	295,911
Held-to-maturity, Amortized Cost	71,213	7,225
Held-to-maturity, Gross Unrealized Gains	129	288
Held-to-maturity, Gross Unrealized Losses	896
Held-to-maturity, Fair value	70,446	7,513
U.S. Treasury securities
Investment Securities
Available-for-sale, Amortized Cost	193,849	18,478
Available-for-sale, Gross Unrealized Gains	107	427
Available-for-sale, Gross Unrealized Losses	2,382
Available-for-sale, Fair Value	191,574	18,905
U.S. Government-sponsored enterprises state and municipals
Investment Securities
Available-for-sale, Amortized Cost	33,435	63,834
Available-for-sale, Gross Unrealized Gains	343	1,354
Available-for-sale, Fair Value	33,778	65,188
Mortgage-backed Securities, U.S. Government agencies
Investment Securities
Available-for-sale, Amortized Cost	1,790	3,553
Available-for-sale, Gross Unrealized Gains	53	154
Available-for-sale, Fair Value	1,843	3,707
Held-to-maturity, Amortized Cost	18,802	21
Held-to-maturity, Gross Unrealized Losses	392
Held-to-maturity, Fair value	18,410	21
Mortgage-backed Securities, U.S. Government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	109,018	79,457
Available-for-sale, Gross Unrealized Gains	939	1,930
Available-for-sale, Gross Unrealized Losses	2,925	136
Available-for-sale, Fair Value	107,032	81,251
Held-to-maturity, Amortized Cost	40,935	355
Held-to-maturity, Gross Unrealized Gains	3	13
Held-to-maturity, Gross Unrealized Losses	448
Held-to-maturity, Fair value	40,490	368
Commercial mortgage-backed Securities, U.S. government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	12,542	12,619
Available-for-sale, Gross Unrealized Gains	406	881
Available-for-sale, Fair Value	12,948	13,500
Corporate Debt Securities
Investment Securities
Available-for-sale, Amortized Cost	3,000	1,000
Available-for-sale, Gross Unrealized Losses	82
Available-for-sale, Fair Value	2,918	1,000
State and Municipals, Taxable
Investment Securities
Available-for-sale, Amortized Cost	69,066	53,297
Available-for-sale, Gross Unrealized Gains	994	2,099
Available-for-sale, Gross Unrealized Losses	1,082	30
Available-for-sale, Fair Value	68,978	55,366
Held-to-maturity, Amortized Cost	11,476
Held-to-maturity, Gross Unrealized Gains	126
Held-to-maturity, Gross Unrealized Losses	56
Held-to-maturity, Fair value	11,546
State and Municipals, Tax-exempt
Investment Securities
Available-for-sale, Amortized Cost	96,412	53,977
Available-for-sale, Gross Unrealized Gains	2,452	3,054
Available-for-sale, Gross Unrealized Losses	614	37
Available-for-sale, Fair Value	$ 98,250	56,994
Held-to-maturity, Amortized Cost		6,849
Held-to-maturity, Gross Unrealized Gains		275
Held-to-maturity, Fair value		$ 7,124

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, 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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