Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	$ 20,346	$ 20,756	$ 19,704	$ 19,693
Charge-offs	(773)	(710)	(1,576)	(1,436)
Recoveries	76	171	215	329
Provision (benefit) for loan losses	1,788	1,905	3,094	3,536
Allowance for loan losses, Ending Balance	21,437	22,122	21,437	22,122
Commercial, industrial, and agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	7,787	6,282	7,341	6,160
Charge-offs	0	0	0	(31)
Recoveries	4	94	8	162
Provision (benefit) for loan losses	317	767	759	852
Allowance for loan losses, Ending Balance	8,108	7,143	8,108	7,143
Commercial Mortgages
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	8,846	10,020	7,490	9,007
Charge-offs	0	0	(2)	0
Recoveries	16	0	1	0
Provision (benefit) for loan losses	676	595	2,049	1,608
Allowance for loan losses, Ending Balance	9,538	10,615	9,538	10,615
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	1,383	2,052	2,156	2,033
Charge-offs	(146)	(77)	(244)	(77)
Recoveries	2	9	67	12
Provision (benefit) for loan losses	164	(84)	(576)	(68)
Allowance for loan losses, Ending Balance	1,403	1,900	1,403	1,900
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	2,040	2,065	2,377	2,179
Charge-offs	(513)	(551)	(1,062)	(1,141)
Recoveries	28	35	74	84
Provision (benefit) for loan losses	586	607	752	1,034
Allowance for loan losses, Ending Balance	2,141	2,156	2,141	2,156
Credit cards
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	105	123	103	120
Charge-offs	(26)	(26)	(52)	(45)
Recoveries	1	17	6	24
Provision (benefit) for loan losses	7	(13)	30	2
Allowance for loan losses, Ending Balance	87	101	87	101
Overdrafts
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses, Beginning Balance	185	214	237	194
Charge-offs	(88)	(56)	(216)	(142)
Recoveries	25	16	59	47
Provision (benefit) for loan losses	38	33	80	108
Allowance for loan losses, Ending Balance	$ 160	$ 207	$ 160	$ 207