Loans - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 886		$ 168
Collectively evaluated for impairment	15,740		14,982
Modified in a troubled debt restructuring	4,811		4,554
Total ending allowance balance	21,437	$ 20,346	19,704	$ 22,122	$ 20,756	$ 19,693
Loans:
Individually evaluated for impairment	3,573		3,292
Collectively evaluated for impairment	2,610,279		2,460,863
Modified in a troubled debt restructuring	12,872		14,626
Total ending loans balance	2,627,269		2,479,348
Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	545		567
Commercial, Industrial, and Agricultural
Ending allowance balance attributable to loans:
Individually evaluated for impairment	222		54
Collectively evaluated for impairment	7,795		7,183
Modified in a troubled debt restructuring	91		104
Total ending allowance balance	8,108	7,787	7,341	7,143	6,282	6,160
Loans:
Individually evaluated for impairment	1,666		1,334
Collectively evaluated for impairment	988,617		910,386
Modified in a troubled debt restructuring	3,346		4,577
Total ending loans balance	993,629		916,297
Commercial, Industrial, and Agricultural | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	0		0
Commercial mortgages
Ending allowance balance attributable to loans:
Individually evaluated for impairment	664		4
Collectively evaluated for impairment	4,154		3,036
Modified in a troubled debt restructuring	4,720		4,450
Total ending allowance balance	9,538	8,846	7,490	10,615	10,020	9,007
Loans:
Individually evaluated for impairment	1,435		1,446
Collectively evaluated for impairment	738,828		685,714
Modified in a troubled debt restructuring	9,526		10,049
Total ending loans balance	750,334		697,776
Commercial mortgages | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	545		567
Residential Real Estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		100
Collectively evaluated for impairment	1,403		2,056
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	1,403	1,383	2,156	1,900	2,052	2,033
Loans:
Individually evaluated for impairment	472		502
Collectively evaluated for impairment	785,882		770,807
Modified in a troubled debt restructuring	0		0
Total ending loans balance	786,354		771,309
Residential Real Estate | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	0		0
Consumer
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	2,141		2,377
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	2,141	2,040	2,377	2,156	2,065	2,179
Loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	89,331		86,035
Modified in a troubled debt restructuring	0		0
Total ending loans balance	89,331		86,035
Consumer | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	0		0
Credit Cards
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	87		103
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	87	105	103	101	123	120
Loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	7,284		7,623
Modified in a troubled debt restructuring	0		0
Total ending loans balance	7,284		7,623
Credit Cards | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	0		0
Overdrafts
Ending allowance balance attributable to loans:
Individually evaluated for impairment	0		10
Collectively evaluated for impairment	160		227
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	160	$ 185	237	$ 207	$ 214	$ 194
Loans:
Individually evaluated for impairment	0		10
Collectively evaluated for impairment	337		298
Modified in a troubled debt restructuring	0		0
Total ending loans balance	337		308
Overdrafts | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	$ 0		$ 0