Investment securities - Maturity Distribution of Debt Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investment securities
Within one year	$ 22,594
After one but within five years	192,724
After five but within ten years	53,280
After ten years	76,895
Available for sale securities, Amortized Cost	345,493
Mortgage-backed and other amortizing securities	104,961
Within one year	21,898
After one but within five years	178,449
After five but within ten years	46,627
After ten years	65,037
Available for sale securities, Fair Value	312,011
Mortgage-backed and other amortizing securities	86,916
Total	$ 398,927	$ 477,703

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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