Carrying values and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Financial Assets
Securities available-for-sale	$ 187,598	$ 187,410
Carrying Reported Amount Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	49,844	50,539
Securities available-for-sale	187,598	187,410
Mutual fund	2,068	1,933
Federal Home Loan Bank of Boston stock	5,030	1,285
Loans held-for-sale
Loans receivable, net	1,234,632	1,213,671
Accrued interest receivable	6,383	6,797
Cash surrender value of life insurance policies	30,571	30,379
Financial Liabilities
Demand (non-interest-bearing)	370,049	395,994
Demand (interest-bearing)	218,902	231,486
Money market	296,974	343,965
Savings and other	236,755	233,578
Certificates of deposit	170,362	153,370
Deposits	1,293,042	1,358,393
Repurchase agreements	3,230	7,228
FHLBB advances	100,000	10,000
Subordinated debt	24,545	24,531
Note payable	117	128
Finance lease liability	4,225	4,262
Accrued interest payable	425	210
Estimate Of Fair Value Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	49,844	50,539
Securities available-for-sale	187,598	187,410
Mutual fund	2,068	1,933
Federal Home Loan Bank of Boston stock	5,030	1,285
Loans held-for-sale
Loans receivable, net	1,193,272	1,172,416
Accrued interest receivable	6,383	6,797
Cash surrender value of life insurance policies	30,571	30,379
Financial Liabilities
Demand (non-interest-bearing)	370,049	395,994
Demand (interest-bearing)	218,902	231,486
Money market	296,974	343,965
Savings and other	236,755	233,578
Certificates of deposit	170,806	153,411
Deposits	1,293,486	1,358,434
Repurchase agreements	3,230	7,228
FHLBB advances	99,999	10,000
Subordinated debt	21,022	21,670
Note payable	114	125
Finance lease liability	3,449	3,546
Accrued interest payable	425	210
Fair Value Inputs Level 1 S A L [Member]
Financial Assets
Cash and cash equivalents	49,844	50,539
Securities available-for-sale	834	833
Mutual fund	2,068	1,933
Federal Home Loan Bank of Boston stock
Loans held-for-sale
Loans receivable, net
Accrued interest receivable
Cash surrender value of life insurance policies
Financial Liabilities
Demand (non-interest-bearing)
Demand (interest-bearing)
Money market
Savings and other
Certificates of deposit
Deposits
Repurchase agreements
FHLBB advances
Subordinated debt
Note payable
Finance lease liability
Accrued interest payable
Fair Value Inputs Level 2 S A L [Member]
Financial Assets
Cash and cash equivalents
Securities available-for-sale	186,764	186,577
Mutual fund
Federal Home Loan Bank of Boston stock	5,030	1,285
Loans held-for-sale
Loans receivable, net
Accrued interest receivable	6,383	6,797
Cash surrender value of life insurance policies	30,571	30,379
Financial Liabilities
Demand (non-interest-bearing)	370,049	395,994
Demand (interest-bearing)	218,902	231,486
Money market	296,974	343,965
Savings and other	236,755	233,578
Certificates of deposit	170,806	153,411
Deposits	1,293,486	1,358,434
Repurchase agreements	3,230	7,228
FHLBB advances	99,999	10,000
Subordinated debt	21,022	21,670
Note payable	114	125
Finance lease liability
Accrued interest payable	425	210
Fair Value Inputs Level 3 S A L [Member]
Financial Assets
Cash and cash equivalents
Securities available-for-sale
Mutual fund
Federal Home Loan Bank of Boston stock
Loans held-for-sale
Loans receivable, net	1,193,272	1,172,416
Accrued interest receivable
Cash surrender value of life insurance policies
Financial Liabilities
Demand (non-interest-bearing)
Demand (interest-bearing)
Money market
Savings and other
Certificates of deposit
Deposits
Repurchase agreements
FHLBB advances
Subordinated debt
Note payable
Finance lease liability	3,449	3,546
Accrued interest payable