Composition of securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale, Cost of Security Sold or Transferred, Method, Specific Identification [Member]
Available-for-sale
U.S. Treasury	$ 15,301
U.S. Government Agency notes	31,623	$ 7,735
Municipal bonds	46,469	25,831
U.S. Government agencies and U.S. Government - sponsored enterprises	74,703	35,240
U.S. Government agencies	20,948	17,054
Corporate bonds	12,250	8,750
Total securities available-for-sale	201,294	94,610
Non-marketable securities
Federal Home Loan Bank of Boston stock	1,397	1,713
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Available-for-sale
U.S. Treasury	12
U.S. Government Agency notes	237	153
Municipal bonds	1,557	1,787
U.S. Government agencies and U.S. Government - sponsored enterprises	643	1,376
U.S. Government agencies	135	400
Corporate bonds	158	166
Total securities available-for-sale	2,742	3,882
Non-marketable securities
Federal Home Loan Bank of Boston stock
Accumulated Net Unrealized Investment Gain Loss 1 [Member]
Available-for-sale
U.S. Treasury	182
U.S. Government Agency notes	256	37
Municipal bonds	204	1
U.S. Government agencies and U.S. Government - sponsored enterprises	805	43
U.S. Government agencies	185
Corporate bonds	8
Total securities available-for-sale	1,640	81
Non-marketable securities
Federal Home Loan Bank of Boston stock
Securities Financing Transaction, Fair Value [Member]
Available-for-sale
U.S. Treasury	15,131
U.S. Government Agency notes	31,604	7,851
Municipal bonds	47,822	27,617
U.S. Government agencies and U.S. Government - sponsored enterprises	74,541	36,573
U.S. Government agencies	20,898	17,454
Corporate bonds	12,400	8,916
Total securities available-for-sale	202,396	98,411
CRA mutual fund	901	917
Non-marketable securities
Federal Home Loan Bank of Boston stock	$ 1,397	$ 1,713