Composition of securities (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-Sale, Cost of Security Sold or Transferred, Method, Specific Identification [Member]
Available-for-sale
U.S. Treasury	$ 20,243	$ 15,301
U.S. Government Agency notes	33,013	31,623
Municipal bonds	51,547	46,469
U.S. Government agencies and U.S. Government- sponsored enterprises	80,554	74,703
U.S. Government agencies	27,202	20,948
Corporate bonds	13,750	12,250
Total securities available-for-sale	226,309	201,294
Non-marketable securities
Federal Home Loan Bank of Boston stock	1,077	1,397
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Available-for-sale
U.S. Treasury		12
U.S. Government Agency notes	119	237
Municipal bonds	52	1,557
U.S. Government agencies and U.S. Government- sponsored enterprises	37	643
U.S. Government agencies	7	135
Corporate bonds	39	158
Total securities available-for-sale	254	2,742
Non-marketable securities
Federal Home Loan Bank of Boston stock
Accumulated Net Unrealized Investment Gain Loss 1 [Member]
Available-for-sale
U.S. Treasury	1,140	182
U.S. Government Agency notes	1,199	256
Municipal bonds	3,300	204
U.S. Government agencies and U.S. Government- sponsored enterprises	3,795	805
U.S. Government agencies	1,289	185
Corporate bonds	188	8
Total securities available-for-sale	10,911	1,640
Non-marketable securities
Federal Home Loan Bank of Boston stock
Securities Financing Transaction, Fair Value [Member]
Available-for-sale
U.S. Treasury	19,103	15,131
U.S. Government Agency notes	31,933	31,604
Municipal bonds	48,299	47,822
U.S. Government agencies and U.S. Government- sponsored enterprises	76,796	74,541
U.S. Government agencies	25,920	20,898
Corporate bonds	13,601	12,400
Total securities available-for-sale	215,652	202,396
CRA mutual fund	862	901
Non-marketable securities
Federal Home Loan Bank of Boston stock	$ 1,077	$ 1,397