Allowance for Loan Losses (the "Allowance") - Roll-forward of allowance by portfolio segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	$ 8,625	$ 7,449	$ 8,053	$ 6,709
Charge-offs	(30)	(50)	(30)	(381)
Recoveries	12	21	351	125
Provision	705	291	938	1,258
Balance at end of period	9,312	7,711	9,312	7,711
Commercial mortgage
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	3,197	3,011	3,209	2,434
Recoveries	1	2	6	6
Provision	257	140	240	713
Balance at end of period	3,455	3,153	3,455	3,153
Home equity lines and loans
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	354	269	323	280
Charge-offs				(137)
Recoveries	2	10	10	14
Provision	(28)	37	(5)	159
Balance at end of period	328	316	328	316
Residential mortgage
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	200	166	191	82
Recoveries	2		4	61
Provision	(30)	14	(23)	37
Balance at end of period	172	180	172	180
Construction
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	2,033	1,438	1,627	1,689
Provision	136	59	542	(192)
Balance at end of period	2,169	1,497	2,169	1,497
Commercial and industrial
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	2,830	2,559	2,690	2,214
Charge-offs	(30)	(50)	(30)	(244)
Recoveries	6	8	328	41
Provision	369	41	187	547
Balance at end of period	3,175	2,558	3,175	2,558
Consumer
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	4	3	3	5
Recoveries	1	1	3	3
Provision	1			(4)
Balance at end of period	6	4	6	4
Leases, net
Roll-Forward of Allowance for Loan and Lease Losses by Portfolio Segment
Balance at beginning of period	7	3	10	5
Provision			(3)	(2)
Balance at end of period	$ 7	$ 3	$ 7	$ 3

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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