Loans - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 2,234		$ 1,943
Collectively evaluated for impairment	21,479		17,172
Modified in a troubled debt restructuring	816		358
Total ending allowance balance	24,529	$ 21,915	19,473	$ 21,437	$ 20,346	$ 19,704
Loans:
Individually evaluated for impairment	17,794		10,953
Collectively evaluated for impairment	3,005,380		2,787,919
Modified in a troubled debt restructuring, collective pool	11,113
Modified in a troubled debt restructuring	11,113		9,802
Total ending loans balance	3,034,788		2,809,197
Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	501		523
Commercial, Industrial  and Agricultural
Ending allowance balance attributable to loans:
Individually evaluated for impairment	642		645
Collectively evaluated for impairment	8,653		7,614
Modified in a troubled debt restructuring	507		28
Total ending allowance balance	9,802	10,532	8,287	8,108	7,787	7,341
Loans:
Individually evaluated for impairment	4,813		8,078
Collectively evaluated for impairment	1,254,203		1,035,494
Modified in a troubled debt restructuring, collective pool	4,505
Modified in a troubled debt restructuring	4,505		3,093
Total ending loans balance	1,263,521		1,046,665
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	1,539		1,264
Collectively evaluated for impairment	7,780		5,358
Modified in a troubled debt restructuring	309		330
Total ending allowance balance	9,628	7,492	6,952	9,538	8,846	7,490
Loans:
Individually evaluated for impairment	12,520		2,410
Collectively evaluated for impairment	845,886		804,360
Modified in a troubled debt restructuring, collective pool	6,494
Modified in a troubled debt restructuring	6,494		6,709
Total ending loans balance	865,401		814,002
Commercial mortgages | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance	0		0
Loans:
Total ending loans balance	501		523
Residential Real Estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	53		34
Collectively evaluated for impairment	2,623		1,465
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	2,676	1,458	1,499	1,403	1,383	2,156
Loans:
Individually evaluated for impairment	461		465
Collectively evaluated for impairment	804,838		813,565
Modified in a troubled debt restructuring, collective pool	114
Modified in a troubled debt restructuring	114		0
Total ending loans balance	805,413		814,030
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	2,140		2,411
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	2,140	2,138	2,411	2,141	2,040	2,377
Loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	93,409		124,785
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring	0		0
Total ending loans balance	93,409		124,785
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	114		84
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	114	112	84	87	105	103
Loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	6,760		7,569
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring	0		0
Total ending loans balance	6,760		7,569
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		0
Collectively evaluated for impairment	169		240
Modified in a troubled debt restructuring	0		0
Total ending allowance balance	169	$ 183	240	$ 160	$ 185	$ 237
Loans:
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	284		2,146
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring			0
Total ending loans balance	284		2,146
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