Allowance for Loan Losses (the "Allowance") - Carrying value based on credit quality indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Evaluated based on credit quality indicators
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	$ 879,669	$ 784,391
Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	847,062	755,681
Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	14,610	18,990
Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	17,997	9,690
Doubtful
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases		30
Commercial mortgage | Evaluated based on credit quality indicators
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	357,418	325,393
Commercial mortgage | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	350,027	320,130
Commercial mortgage | Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	3,437	3,713
Commercial mortgage | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	3,954	1,550
Home equity lines and loans | Evaluated based on credit quality indicators
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	83,412	82,286
Home equity lines and loans | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	83,155	82,121
Home equity lines and loans | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	257	165
Construction | Evaluated based on credit quality indicators
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	154,463	116,906
Construction | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	151,663	114,249
Construction | Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	2,774	2,657
Construction | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	26
Commercial and industrial | Evaluated based on credit quality indicators
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	284,376	259,806
Commercial and industrial | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	262,217	239,181
Commercial and industrial | Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	8,399	12,620
Commercial and industrial | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	$ 13,760	7,975
Commercial and industrial | Doubtful
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases		$ 30