Allowance for Loan and Lease Losses - Credit Quality Indicators by Class of Residential Real Estate and Consumer Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	$ 1,361,676	$ 1,314,210
Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	44,033	51,854
Performing | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,351,890	1,306,211
Performing | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	41,548	49,136
Nonperforming | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	9,786	7,999
Nonperforming | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	2,485	2,718
Residential real estate | Home equity | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	209,168	212,812
Residential real estate | Home equity | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	22,433	28,444
Residential real estate | Mortgages | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,086,065	1,039,040
Residential real estate | Mortgages | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	20,740	22,645
Residential real estate | Performing | Home equity | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	207,571	211,275
Residential real estate | Performing | Home equity | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	21,229	26,840
Residential real estate | Performing | Mortgages | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,078,129	1,032,932
Residential real estate | Performing | Mortgages | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	19,459	21,531
Residential real estate | Nonperforming | Home equity | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,597	1,537
Residential real estate | Nonperforming | Home equity | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,204	1,604
Residential real estate | Nonperforming | Mortgages | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	7,936	6,108
Residential real estate | Nonperforming | Mortgages | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,281	1,114
Consumer and other | Indirect | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	11,963	12,144
Consumer and other | Indirect | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Consumer and other | Other | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	54,480	50,214
Consumer and other | Other | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	859	765
Consumer and other | Performing | Indirect | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	11,779	11,866
Consumer and other | Performing | Indirect | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Consumer and other | Performing | Other | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	54,411	50,138
Consumer and other | Performing | Other | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	859	765
Consumer and other | Nonperforming | Indirect | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	184	278
Consumer and other | Nonperforming | Indirect | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Consumer and other | Nonperforming | Other | Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	69	76
Consumer and other | Nonperforming | Other | Total Acquired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	$ 0	$ 0