Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	$ 21,437	$ 22,122	$ 19,704	$ 19,693
Charge-offs	(3,511)	(813)	(5,087)	(2,249)
Recoveries	163	106	378	435
Provision (benefit) for loan losses	2,118	1,095	5,212	4,631
Allowance for loan losses, Ending Balance	20,207	22,510	20,207	22,510
Commercial, industrial, and agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	8,108	7,143	7,341	6,160
Charge-offs	(160)	(30)	(160)	(61)
Recoveries	5	3	13	165
Provision (benefit) for loan losses	997	(536)	1,756	316
Allowance for loan losses, Ending Balance	8,950	6,580	8,950	6,580
Commercial Mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	9,538	10,615	7,490	9,007
Charge-offs	(2,650)	0	(2,652)	0
Recoveries	65	0	66	0
Provision (benefit) for loan losses	30	682	2,079	2,290
Allowance for loan losses, Ending Balance	6,983	11,297	6,983	11,297
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	1,403	1,900	2,156	2,033
Charge-offs	(38)	(212)	(282)	(289)
Recoveries	5	55	72	67
Provision (benefit) for loan losses	116	235	(460)	167
Allowance for loan losses, Ending Balance	1,486	1,978	1,486	1,978
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	2,141	2,156	2,377	2,179
Charge-offs	(547)	(469)	(1,609)	(1,610)
Recoveries	58	28	132	112
Provision (benefit) for loan losses	693	608	1,445	1,642
Allowance for loan losses, Ending Balance	2,345	2,323	2,345	2,323
Credit cards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	87	101	103	120
Charge-offs	(3)	(8)	(55)	(53)
Recoveries	6	3	12	27
Provision (benefit) for loan losses	15	11	45	13
Allowance for loan losses, Ending Balance	105	107	105	107
Overdrafts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	160	207	237	194
Charge-offs	(113)	(94)	(329)	(236)
Recoveries	24	17	83	64
Provision (benefit) for loan losses	267	95	347	203
Allowance for loan losses, Ending Balance	$ 338	$ 225	$ 338	$ 225