Loans - Allowance for Loan Losses and Recorded Investment in Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Ending allowance balance attributable to loans:
Individually evaluated for impairment	$ 4,804	$ 1,943
Collectively evaluated for impairment	16,761	17,172
Modified in a troubled debt restructuring	350	358
Total ending allowance balance	21,915	19,473	$ 20,346	$ 19,704
Loans:
Individually evaluated for impairment	21,295	10,953
Collectively evaluated for impairment	2,823,802	2,787,919
Modified in a troubled debt restructuring, collective pool	9,597
Modified in a troubled debt restructuring	9,597	9,802
Total ending loans balance	2,855,206	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	512	523
Commercial, Industrial and Agricultural
Ending allowance balance attributable to loans:
Individually evaluated for impairment	3,489	645
Collectively evaluated for impairment	7,009	7,614
Modified in a troubled debt restructuring	34	28
Total ending allowance balance	10,532	8,287	7,787	7,341
Loans:
Individually evaluated for impairment	8,663	8,078
Collectively evaluated for impairment	1,079,220	1,035,494
Modified in a troubled debt restructuring, collective pool	3,032
Modified in a troubled debt restructuring	3,032	3,093
Total ending loans balance	1,090,915	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	1,264	1,264
Collectively evaluated for impairment	5,912	5,358
Modified in a troubled debt restructuring	316	330
Total ending allowance balance	7,492	6,952	8,846	7,490
Loans:
Individually evaluated for impairment	12,172	2,410
Collectively evaluated for impairment	826,966	804,360
Modified in a troubled debt restructuring, collective pool	6,565
Modified in a troubled debt restructuring	6,565	6,709
Total ending loans balance	846,215	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	512	523
Residential Real Estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment	51	34
Collectively evaluated for impairment	1,407	1,465
Modified in a troubled debt restructuring	0	0
Total ending allowance balance	1,458	1,499	1,383	2,156
Loans:
Individually evaluated for impairment	460	465
Collectively evaluated for impairment	814,197	813,565
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring	0	0
Total ending loans balance	814,657	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	2,138	2,411
Modified in a troubled debt restructuring	0	0
Total ending allowance balance	2,138	2,411	2,040	2,377
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	94,425	124,785
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring	0	0
Total ending loans balance	94,425	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	112	84
Modified in a troubled debt restructuring	0	0
Total ending allowance balance	112	84	105	103
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	8,683	7,569
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring	0	0
Total ending loans balance	8,683	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	183	240
Modified in a troubled debt restructuring	0	0
Total ending allowance balance	183	240	$ 185	$ 237
Loans:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	311	2,146
Modified in a troubled debt restructuring, collective pool	0
Modified in a troubled debt restructuring		0
Total ending loans balance	311	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