Loans and Leases - Non-performing Loans and Leases (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	$ 8,990	$ 8,579
Purchased credit impaired became non-performing subsequent to acquisition	393	167
Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	5,397	3,745
Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	3,593	4,834
Commercial mortgage
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	735	872
Commercial mortgage | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	0	90
Commercial mortgage | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	735	782
Home equity loans and lines
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	1,933	1,481
Home equity loans and lines | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	1,692	1,221
Home equity loans and lines | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	241	260
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	2,770	4,417
Residential mortgage | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	1,968	1,505
Residential mortgage | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	802	2,912
Construction
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	291	0
Construction | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	291	0
Construction | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	0	0
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	1,782	1,706
Commercial and industrial | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	925	826
Commercial and industrial | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	857	880
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	117	0
Consumer | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	42	0
Consumer | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	75	0
Leases
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	1,362	103
Leases | Originated
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	479	103
Leases | Acquired
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual loans and leases	$ 883	$ 0