Allowance for Loan and Lease Losses (the "Allowance") - Carrying value based on credit quality indicators (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 804,473	$ 784,391
Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	772,235	755,681
Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	17,961	18,990
Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	14,247	9,690
Doubtful
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	30	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	325,843	325,393
Commercial mortgage | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	320,616	320,130
Commercial mortgage | Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	3,347	3,713
Commercial mortgage | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	1,880	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	81,939	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	81,776	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	163	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	127,663	116,906
Construction | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	125,000	114,249
Construction | Special mention
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	2,663	2,657
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	269,028	259,806
Commercial and industrial | Pass
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	244,843	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	11,951	12,620
Commercial and industrial | Substandard
Loans and Leases by Credit Ratings
Carry value of loans and leases excluding residential mortgage, consumer and leases	12,204	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	$ 30