Carrying values and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financial Assets
Securities available-for-sale	$ 177,477	$ 187,410
Carrying Reported Amount Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	54,057	50,539
Securities available-for-sale	177,477	187,410
Mutual fund	2,020	1,933
Federal Home Loan Bank of Boston stock	1,488	1,285
Loans held-for-sale
Loans receivable, net	1,237,511	1,213,671
Accrued interest receivable	6,546	6,797
Cash surrender value of life insurance policies	30,248	30,379
Financial Liabilities
Demand (non-interest-bearing)	353,794	395,994
Demand (interest-bearing)	219,483	231,486
Money market	361,004	343,965
Savings and other	218,339	233,578
Certificates of deposit	207,330	153,370
Deposits	1,359,950	1,358,393
Repurchase agreements	7,492	7,228
FHLBB advances	20,000	10,000
Subordinated debt	24,559	24,531
Note payable	106	128
Finance lease liability	4,189	4,262
Accrued interest payable	721	210
Estimate Of Fair Value Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	54,057	50,539
Securities available-for-sale	177,477	187,410
Mutual fund	2,020	1,933
Federal Home Loan Bank of Boston stock	1,488	1,285
Loans held-for-sale
Loans receivable, net	1,180,881	1,172,416
Accrued interest receivable	6,546	6,797
Cash surrender value of life insurance policies	30,248	30,379
Financial Liabilities
Demand (non-interest-bearing)	353,794	395,994
Demand (interest-bearing)	219,483	231,486
Money market	361,004	343,965
Savings and other	218,339	233,578
Certificates of deposit	206,311	153,411
Deposits	1,358,931	1,358,434
Repurchase agreements	7,492	7,228
FHLBB advances	20,000	10,000
Subordinated debt	20,257	21,670
Note payable	103	125
Finance lease liability	3,357	3,546
Accrued interest payable	721	210
Fair Value Inputs Level 1 S A L [Member]
Financial Assets
Cash and cash equivalents	54,057	50,539
Securities available-for-sale	803	833
Mutual fund	2,020	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	176,674	186,577
Mutual fund
Federal Home Loan Bank of Boston stock	1,488	1,285
Loans held-for-sale
Loans receivable, net
Accrued interest receivable	6,546	6,797
Cash surrender value of life insurance policies	30,248	30,379
Financial Liabilities
Demand (non-interest-bearing)	353,794	395,994
Demand (interest-bearing)	219,483	231,486
Money market	361,004	343,965
Savings and other	218,339	233,578
Certificates of deposit	206,311	153,411
Deposits	1,358,931	1,358,434
Repurchase agreements	7,492	7,228
FHLBB advances	20,000	10,000
Subordinated debt	20,257	21,670
Note payable	103	125
Finance lease liability
Accrued interest payable	721	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	1,180,881	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	3,357	3,546
Accrued interest payable