Loans and Leases - Allowance for Loan and Leases Losses Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	$ 17,662	$ 17,107	$ 17,525	$ 17,486
Charge-offs	(1,477)	(737)	(2,431)	(1,507)
Recoveries	76	112	137	212
Provision for loan and lease losses	3,137	(83)	4,167	208
Balance	19,398	16,399	19,398	16,399
Commercial mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	7,174	6,410	7,550	6,227
Charge-offs	(16)	0	(16)	0
Recoveries	3	3	6	6
Provision for loan and lease losses	872	195	493	375
Balance	8,033	6,608	8,033	6,608
Home equity loans and lines
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,045	1,243	1,086	1,255
Charge-offs	(200)	(169)	(225)	(606)
Recoveries	1	0	1	0
Provision for loan and lease losses	87	140	71	565
Balance	933	1,214	933	1,214
Residential mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,898	1,798	1,926	1,917
Charge-offs	0	(43)	0	(70)
Recoveries	1	0	1	0
Provision for loan and lease losses	34	21	6	(71)
Balance	1,933	1,776	1,933	1,776
Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	844	2,195	937	2,233
Charge-offs	0	0	0	0
Recoveries	1	1	2	2
Provision for loan and lease losses	313	(1,085)	219	(1,124)
Balance	1,158	1,111	1,158	1,111
Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	5,361	4,747	5,038	5,142
Charge-offs	(467)	(200)	(750)	(259)
Recoveries	0	15	1	15
Provision for loan and lease losses	778	251	1,383	(85)
Balance	5,672	4,813	5,672	4,813
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	291	135	246	153
Charge-offs	(43)	(18)	(92)	(59)
Recoveries	2	2	3	4
Provision for loan and lease losses	39	58	132	79
Balance	289	177	289	177
Leases
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,049	579	742	559
Charge-offs	(751)	(307)	(1,348)	(513)
Recoveries	68	91	123	185
Provision for loan and lease losses	1,014	337	1,863	469
Balance	1,380	700	1,380	700
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	0	0	0	0
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision for loan and lease losses	0	0	0	0
Balance	$ 0	$ 0	$ 0	$ 0