Loans - Modification Statuses by Portfolio Segment (Details) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($) loan	Dec. 31, 2019 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	78	82	81
Percentage of loans receivable, by type	100.00%	100.00%	100.00%
Balance \| $	$ 1,436,646	$ 1,263,459	$ 1,297,075
Commercial/Municipal Portfolio Segment \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	582
Percentage of loans receivable, by type	100.00%
Balance \| $	$ 228,069
Percentage of balance	100.00%
Commercial/Municipal Portfolio Segment \| Paid Off \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	34
Percentage of loans receivable, by type	6.00%
Balance \| $	$ 6,031
Percentage of balance	3.00%
Commercial/Municipal Portfolio Segment \| Subsequent Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	41
Percentage of loans receivable, by type	7.00%
Balance \| $	$ 20,443
Percentage of balance	9.00%
Commercial/Municipal Portfolio Segment \| Still in Original Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	55
Percentage of loans receivable, by type	9.00%
Balance \| $	$ 30,188
Percentage of balance	13.00%
Commercial/Municipal Portfolio Segment \| Out of Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	452
Percentage of loans receivable, by type	78.00%
Balance \| $	$ 171,407
Percentage of balance	75.00%
Residential Portfolio Segment \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	350
Percentage of loans receivable, by type	100.00%
Balance \| $	$ 50,473
Percentage of balance	100.00%
Residential Portfolio Segment \| Paid Off \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	17
Percentage of loans receivable, by type	5.00%
Balance \| $	$ 3,102
Percentage of balance	6.00%
Residential Portfolio Segment \| Subsequent Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	97
Percentage of loans receivable, by type	28.00%
Balance \| $	$ 13,857
Percentage of balance	27.00%
Residential Portfolio Segment \| Still in Original Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	125
Percentage of loans receivable, by type	35.00%
Balance \| $	$ 15,565
Percentage of balance	31.00%
Residential Portfolio Segment \| Out of Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	111
Percentage of loans receivable, by type	32.00%
Balance \| $	$ 17,949
Percentage of balance	36.00%
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	1	0	0
Percentage of loans receivable, by type	1.90%	2.10%	2.00%
Balance \| $	$ 27,323	$ 25,919	$ 26,503
Consumer \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	64
Percentage of loans receivable, by type	100.00%
Balance \| $	$ 1,120
Percentage of balance	100.00%
Consumer \| Paid Off \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	8
Percentage of loans receivable, by type	13.00%
Balance \| $	$ 95
Percentage of balance	9.00%
Consumer \| Subsequent Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	0
Percentage of loans receivable, by type	0.00%
Balance \| $	$ 0
Percentage of balance	0.00%
Consumer \| Still in Original Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	52
Percentage of loans receivable, by type	81.00%
Balance \| $	$ 967
Percentage of balance	86.00%
Consumer \| Out of Modification \| Exemption from Troubled Debt Restructure Designation, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Units \| loan	4
Percentage of loans receivable, by type	6.00%
Balance \| $	$ 58
Percentage of balance	5.00%