Loans and Leases - Allowance for Loan and Leases Losses Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	$ 19,398	$ 16,399	$ 17,525	$ 17,486
Charge-offs	(1,560)	(906)	(3,991)	(2,414)
Recoveries	182	178	319	391
Provision for loan and lease losses	664	1,333	4,831	1,541
Balance	18,684	17,004	18,684	17,004
Commercial mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	8,033	6,608	7,550	6,227
Charge-offs	(58)	0	(74)	0
Recoveries	2	3	8	9
Provision for loan and lease losses	(433)	721	60	1,096
Balance	7,544	7,332	7,544	7,332
Home equity loans and lines
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	933	1,214	1,086	1,255
Charge-offs	0	(69)	(225)	(676)
Recoveries	0	0	1	0
Provision for loan and lease losses	(41)	(53)	30	513
Balance	892	1,092	892	1,092
Residential mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,933	1,776	1,926	1,917
Charge-offs	(42)	(88)	(42)	(158)
Recoveries	54	85	55	85
Provision for loan and lease losses	(127)	48	(121)	(23)
Balance	1,818	1,821	1,818	1,821
Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,158	1,111	937	2,233
Charge-offs	0	0	0	0
Recoveries	0	1	1	3
Provision for loan and lease losses	83	(182)	303	(1,306)
Balance	1,241	930	1,241	930
Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	5,672	4,813	5,038	5,142
Charge-offs	(319)	(301)	(1,069)	(560)
Recoveries	16	2	17	18
Provision for loan and lease losses	(64)	366	1,319	280
Balance	5,305	4,880	5,305	4,880
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	289	177	246	153
Charge-offs	(73)	(37)	(165)	(96)
Recoveries	2	1	5	5
Provision for loan and lease losses	100	69	232	148
Balance	318	210	318	210
Leases
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance	1,380	700	742	559
Charge-offs	(1,068)	(411)	(2,416)	(924)
Recoveries	108	86	232	271
Provision for loan and lease losses	1,146	364	3,008	833
Balance	1,566	739	1,566	739
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