Commitments and Contingencies (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) loan
Financial instruments whose contract amount represents credit risk [Abstract]
Deposits	$ 657,154,000		$ 657,154,000		$ 779,506,000
Interest income	7,649,000	$ 7,345,000	23,579,000	$ 21,256,000
Noninterest Income	2,813,000	2,261,000	7,688,000	6,122,000
Standby Letters of Credit [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	3,577,000		$ 3,577,000		3,321,000
Letters of credit expiry period			12 months
Letters of credit renewal period			1 year
Current liability for guarantees	13,000		$ 13,000		42,000
Home Equity Lines of Credit [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	17,375,000		$ 17,375,000		17,015,000
Loan expiry period			10 years
Unadvanced Construction Commitments [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	79,385,000		$ 79,385,000		75,326,000
Mortgage Loan Commitments [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	1,628,000		1,628,000		1,649,000
Lines of Credit [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	21,990,000		$ 21,990,000		$ 20,990,000
Residential Mortgage [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Number of residential mortgage loan commitments | loan			3		3
Residential mortgage loan commitments	1,600,000		$ 1,600,000		$ 1,600,000
Loans Sold and Serviced with Limited Repurchase Provisions [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Off-balance sheet credit risk	66,194,000		66,194,000		49,623,000
Repurchases of loans previously sold			$ 0	0
Loans Sold and Serviced with Limited Repurchase Provisions [Member] | Minimum [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Period of delinquency under repurchase agreement			120 days
Loans Sold and Serviced with Limited Repurchase Provisions [Member] | Maximum [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Period of delinquency under repurchase agreement			180 days
Business activities with medical-use cannabis customers [Member] | Cannabis Customers [Member]
Financial instruments whose contract amount represents credit risk [Abstract]
Deposits	20,600,000		$ 20,600,000		17,000,000
Loan balances	$ 15,400,000		$ 15,400,000		$ 14,100,000
Percentage of deposits in total deposits	3.10%		3.10%		2.20%
Percentage of loans in total loans	2.30%		2.30%		2.10%
Interest income	$ 227,000	231,000	$ 655,000	541,000
Noninterest Income	515,000	376,000	1,500,000	921,000
Volume of deposits accepted	$ 70,500,000	$ 41,500,000	$ 176,600,000	$ 70,800,000