Allowance for Loan Losses and Credit Quality - Allowance for Loan Losses, by Class of Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	$ 8,336	$ 8,429	$ 8,336	$ 8,271
Provision (credit) for loan losses	0	75	0	225
Recoveries of amounts charged off	5	1	6	9
Balance, before amounts charged off	8,341	8,505	8,342	8,505
Amounts charged off	(1)	0	(2)	0
Balance end of period	8,340	8,505	8,340	8,505
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	2,224	1,996	2,068	1,776
Provision (credit) for loan losses	15	86	171	298
Recoveries of amounts charged off	0	0	0	8
Balance, before amounts charged off	2,239	2,082	2,239	2,082
Amounts charged off	0	0	0	0
Balance end of period	2,239	2,082	2,239	2,082
Construction real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	843	881	837	763
Provision (credit) for loan losses	114	143	120	261
Recoveries of amounts charged off	0	0	0	0
Balance, before amounts charged off	957	1,024	957	1,024
Amounts charged off	0	0	0	0
Balance end of period	957	1,024	957	1,024
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	3,997	4,133	4,122	4,199
Provision (credit) for loan losses	7	(22)	(118)	(88)
Recoveries of amounts charged off	0	0	0	0
Balance, before amounts charged off	4,004	4,111	4,004	4,111
Amounts charged off	0	0	0	0
Balance end of period	4,004	4,111	4,004	4,111
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	289	443	275	458
Provision (credit) for loan losses	28	(18)	42	(33)
Recoveries of amounts charged off	2	0	2	0
Balance, before amounts charged off	319	425	319	425
Amounts charged off	(1)	0	(1)	0
Balance end of period	318	425	318	425
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	10	13	11	15
Provision (credit) for loan losses	(3)	(2)	(4)	(4)
Recoveries of amounts charged off	3	1	4	1
Balance, before amounts charged off	10	12	11	12
Amounts charged off	0	0	(1)	0
Balance end of period	10	12	10	12
Municipal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	88	199	86	214
Provision (credit) for loan losses	(61)	(118)	(59)	(133)
Recoveries of amounts charged off	0	0	0	0
Balance, before amounts charged off	27	81	27	81
Amounts charged off	0	0	0	0
Balance end of period	27	81	27	81
Unallocated
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance beginning of period	885	764	937	846
Provision (credit) for loan losses	(100)	6	(152)	(76)
Recoveries of amounts charged off	0	0	0	0
Balance, before amounts charged off	785	770	785	770
Amounts charged off	0	0	0	0
Balance end of period	$ 785	$ 770	$ 785	$ 770