Carrying values and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Carrying Reported Amount Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	$ 50,539	$ 175,335
Securities available-for-sale	187,410	202,396
Mutual fund	1,933	901
Federal Home Loan Bank of Boston stock	1,285	1,397
Loans held-for-sale		2,684
Loans receivable, net	1,213,671	1,066,750
Accrued interest receivable	6,797	6,260
Cash surrender value of life insurance policies	30,379	27,738
Financial Liabilities
Demand (non-interest-bearing)	395,994	416,073
Demand (interest-bearing)	231,486	233,600
Money market	343,965	330,436
Savings and other	233,578	237,075
Certificates of deposit	153,370	119,009
Deposits	1,358,393	1,336,193
Repurchase agreements	7,228	11,430
FHLBB advances	10,000	7,656
Subordinated debt	24,531	24,474
Note payable	128	170
Finance lease liability	4,262	4,107
Accrued interest payable	210	49
Interest bearing time deposits with financial institutions		750
Derivative financial instruments		18
Estimate Of Fair Value Fair Value Disclosure S A L [Member]
Financial Assets
Cash and cash equivalents	50,539	175,335
Securities available-for-sale	187,410	202,396
Mutual fund	1,933	901
Federal Home Loan Bank of Boston stock	1,285	1,397
Loans held-for-sale		2,721
Loans receivable, net	1,172,416	1,066,733
Accrued interest receivable	6,797	6,260
Cash surrender value of life insurance policies	30,379	27,738
Financial Liabilities
Demand (non-interest-bearing)	395,994	416,073
Demand (interest-bearing)	231,486	233,600
Money market	343,965	330,436
Savings and other	233,578	237,075
Certificates of deposit	153,411	119,716
Deposits	1,358,434	1,336,900
Repurchase agreements	7,228	11,430
FHLBB advances	10,000	7,714
Subordinated debt	21,670	24,409
Note payable	125	171
Finance lease liability	3,546	4,223
Accrued interest payable	210	49
Interest bearing time deposits with financial institutions		750
Derivative financial instruments		18
Fair Value Inputs Level 1 S A L [Member]
Financial Assets
Cash and cash equivalents	50,539	175,335
Securities available-for-sale	833
Mutual fund	1,933	901
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
Interest bearing time deposits with financial institutions		750
Derivative financial instruments
Fair Value Inputs Level 2 S A L [Member]
Financial Assets
Cash and cash equivalents
Securities available-for-sale	186,577	202,396
Mutual fund
Federal Home Loan Bank of Boston stock	1,285	1,397
Loans held-for-sale
Loans receivable, net
Accrued interest receivable	6,797	6,260
Cash surrender value of life insurance policies	30,379	27,738
Financial Liabilities
Demand (non-interest-bearing)	395,994	416,073
Demand (interest-bearing)	231,486	233,600
Money market	343,965	330,436
Savings and other	233,578	237,075
Certificates of deposit	153,411	119,716
Deposits	1,358,434	1,336,900
Repurchase agreements	7,228	11,430
FHLBB advances	10,000	7,714
Subordinated debt	21,670	24,409
Note payable	125	171
Finance lease liability
Accrued interest payable	210	49
Interest bearing time deposits with financial institutions
Derivative financial instruments		18
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		2,721
Loans receivable, net	1,172,416	1,066,733
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	3,546	4,223
Accrued interest payable
Interest bearing time deposits with financial institutions
Derivative financial instruments