Allowance for Loan and Lease Losses - Credit Quality Indicators by Class of Residential Real Estate (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Originated Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	$ 1,314,210	$ 1,215,883
Originated Loans and Leases | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,306,211	1,208,259
Originated Loans and Leases | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	7,999	7,624
Originated Loans and Leases | Residential real estate | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	212,812	209,277
Originated Loans and Leases | Residential real estate | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,039,040	947,378
Originated Loans and Leases | Residential real estate | Performing | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	211,275	207,261
Originated Loans and Leases | Residential real estate | Performing | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,032,932	941,936
Originated Loans and Leases | Residential real estate | Nonperforming | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,537	2,016
Originated Loans and Leases | Residential real estate | Nonperforming | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	6,108	5,442
Originated Loans and Leases | Consumer and other | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	12,144	14,835
Originated Loans and Leases | Consumer and other | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	50,214	44,393
Originated Loans and Leases | Consumer and other | Performing | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	11,866	14,669
Originated Loans and Leases | Consumer and other | Performing | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	50,138	44,393
Originated Loans and Leases | Consumer and other | Nonperforming | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	278	166
Originated Loans and Leases | Consumer and other | Nonperforming | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	76	0
Acquired Loans and Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	51,854	63,986
Acquired Loans and Leases | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	49,136	62,383
Acquired Loans and Leases | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	2,718	1,603
Acquired Loans and Leases | Residential real estate | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	28,444	37,737
Acquired Loans and Leases | Residential real estate | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	22,645	25,423
Acquired Loans and Leases | Residential real estate | Performing | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	26,840	37,074
Acquired Loans and Leases | Residential real estate | Performing | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	21,531	24,483
Acquired Loans and Leases | Residential real estate | Nonperforming | Residential Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,604	663
Acquired Loans and Leases | Residential real estate | Nonperforming | Residential Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	1,114	940
Acquired Loans and Leases | Consumer and other | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Acquired Loans and Leases | Consumer and other | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	765	826
Acquired Loans and Leases | Consumer and other | Performing | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Acquired Loans and Leases | Consumer and other | Performing | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	765	826
Acquired Loans and Leases | Consumer and other | Nonperforming | Consumer Indirect
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	0	0
Acquired Loans and Leases | Consumer and other | Nonperforming | Consumer Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases, gross	$ 0	$ 0