Loans - Allowance for Credit/Loan Losses and Recorded Investment in Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Ending allowance balance attributable to loans:
Individually evaluated for impairment			$ 1,943
Collectively evaluated for impairment			17,172
Modified in a troubled debt restructuring			358
Total ending allowance balance	$ 34,340	$ 19,473	19,473	$ 19,704	$ 19,693
Loans:
Individually evaluated for impairment			10,953
Collectively evaluated for impairment			2,787,919
Modified in a troubled debt restructuring			9,802
Total ending loans balance	3,371,789		2,809,197
Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			523
Commercial, industrial, and agricultural
Ending allowance balance attributable to loans:
Individually evaluated for impairment			645
Collectively evaluated for impairment			7,614
Modified in a troubled debt restructuring			28
Total ending allowance balance		8,287	8,287	7,341	6,160
Loans:
Individually evaluated for impairment			8,078
Collectively evaluated for impairment			1,035,494
Modified in a troubled debt restructuring			3,093
Total ending loans balance			1,046,665
Commercial, industrial, and agricultural | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			0
Commercial mortgages
Ending allowance balance attributable to loans:
Individually evaluated for impairment			1,264
Collectively evaluated for impairment			5,358
Modified in a troubled debt restructuring			330
Total ending allowance balance		6,952	6,952	7,490	9,007
Loans:
Individually evaluated for impairment			2,410
Collectively evaluated for impairment			804,360
Modified in a troubled debt restructuring			6,709
Total ending loans balance			814,002
Commercial mortgages | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			523
Residential Real Estate
Ending allowance balance attributable to loans:
Individually evaluated for impairment			34
Collectively evaluated for impairment			1,465
Modified in a troubled debt restructuring			0
Total ending allowance balance		1,499	1,499	2,156	2,033
Loans:
Individually evaluated for impairment			465
Collectively evaluated for impairment			813,565
Modified in a troubled debt restructuring			0
Total ending loans balance			814,030
Residential Real Estate | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			0
Consumer
Ending allowance balance attributable to loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			2,411
Modified in a troubled debt restructuring			0
Total ending allowance balance		2,411	2,411	2,377	2,179
Loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			124,785
Modified in a troubled debt restructuring			0
Total ending loans balance			124,785
Consumer | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			0
Credit Cards
Ending allowance balance attributable to loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			84
Modified in a troubled debt restructuring			0
Total ending allowance balance	66	84	84	103	120
Loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			7,569
Modified in a troubled debt restructuring			0
Total ending loans balance	8,115		7,569
Credit Cards | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			0
Overdrafts
Ending allowance balance attributable to loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			240
Modified in a troubled debt restructuring			0
Total ending allowance balance	244	$ 240	240	$ 237	$ 194
Loans:
Individually evaluated for impairment			0
Collectively evaluated for impairment			2,146
Modified in a troubled debt restructuring			0
Total ending loans balance	$ 336		2,146
Overdrafts | Acquired with deteriorated credit quality
Ending allowance balance attributable to loans:
Total ending allowance balance			0
Loans:
Total ending loans balance			$ 0