Investment securities - Amortized Cost and Fair Value of Investment Securities Aggregated by Investment Category (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Investment Securities
Available-for-sale, Amortized Cost	$ 552,172	$ 519,112
Available-for-sale, Gross Unrealized Gains	2	5,294
Available-for-sale, Gross Unrealized Losses	74,584	7,085
Available-for-sale, Fair Value	477,590	517,321
Held-to-maturity, Amortized Cost	92,771	71,213
Held-to-maturity, Gross Unrealized Gains		129
Held-to-maturity, Gross Unrealized Losses	14,259	896
Held-to-maturity, Fair value	78,512	70,446
U.S. Treasury securities
Investment Securities
Available-for-sale, Amortized Cost	247,812	193,849
Available-for-sale, Gross Unrealized Gains		107
Available-for-sale, Gross Unrealized Losses	23,476	2,382
Available-for-sale, Fair Value	224,336	191,574
U.S. Government-sponsored enterprises state and municipals
Investment Securities
Available-for-sale, Amortized Cost	16,976	33,435
Available-for-sale, Gross Unrealized Gains		343
Available-for-sale, Gross Unrealized Losses	625
Available-for-sale, Fair Value	16,351	33,778
State and Municipals, Taxable
Investment Securities
Available-for-sale, Amortized Cost	69,913	69,066
Available-for-sale, Gross Unrealized Gains	1	994
Available-for-sale, Gross Unrealized Losses	13,680	1,082
Available-for-sale, Fair Value	56,234	68,978
State and Municipals, Tax-exempt
Investment Securities
Available-for-sale, Amortized Cost	100,078	96,412
Available-for-sale, Gross Unrealized Gains	1	2,452
Available-for-sale, Gross Unrealized Losses	15,493	614
Available-for-sale, Fair Value	84,586	98,250
State and Municipals Tax-exempt Bonds
Investment Securities
Held-to-maturity, Amortized Cost	11,247	11,476
Held-to-maturity, Gross Unrealized Gains		126
Held-to-maturity, Gross Unrealized Losses	1,286	56
Held-to-maturity, Fair value	9,961	11,546
Mortgage-backed Securities, U.S. Government agencies
Investment Securities
Available-for-sale, Amortized Cost	1,130	1,790
Available-for-sale, Gross Unrealized Gains		53
Available-for-sale, Gross Unrealized Losses	39
Available-for-sale, Fair Value	1,091	1,843
Held-to-maturity, Amortized Cost	17,732	18,802
Held-to-maturity, Gross Unrealized Losses	2,679	392
Held-to-maturity, Fair value	15,053	18,410
Mortgage-backed Securities, U.S. Government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	100,020	109,018
Available-for-sale, Gross Unrealized Gains		939
Available-for-sale, Gross Unrealized Losses	20,312	2,925
Available-for-sale, Fair Value	79,708	107,032
Held-to-maturity, Amortized Cost	63,792	40,935
Held-to-maturity, Gross Unrealized Gains		3
Held-to-maturity, Gross Unrealized Losses	10,294	448
Held-to-maturity, Fair value	53,498	40,490
Commercial mortgage-backed Securities, U.S. government-sponsored enterprises
Investment Securities
Available-for-sale, Amortized Cost	12,243	12,542
Available-for-sale, Gross Unrealized Gains		406
Available-for-sale, Gross Unrealized Losses	564
Available-for-sale, Fair Value	11,679	12,948
Corporate Debt Securities
Investment Securities
Available-for-sale, Amortized Cost	4,000	3,000
Available-for-sale, Gross Unrealized Losses	395	82
Available-for-sale, Fair Value	$ 3,605	$ 2,918

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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