Loans and Allowance - Past Due Aging of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Past Due [Line Items]
Loans	$ 9,041,576	$ 9,243,174
Loans > 90 Days or More Past Due And Accruing	157	746
Current
Financing Receivable, Past Due [Line Items]
Loans	9,002,702	9,170,399
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	12,170	19,638
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	3,541	11,187
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	23,163	41,950
Commercial and industrial loans
Financing Receivable, Past Due [Line Items]
Loans	2,573,615	2,776,699
Loans > 90 Days or More Past Due And Accruing	1	594
Commercial and industrial loans | Current
Financing Receivable, Past Due [Line Items]
Loans	2,554,111	2,761,473
Commercial and industrial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	2,667	5,866
Commercial and industrial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	507	6,571
Commercial and industrial loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	16,330	2,789
Agricultural land, production and other loans to farmers
Financing Receivable, Past Due [Line Items]
Loans	240,686	281,884
Loans > 90 Days or More Past Due And Accruing	0	0
Agricultural land, production and other loans to farmers | Current
Financing Receivable, Past Due [Line Items]
Loans	240,660	280,615
Agricultural land, production and other loans to farmers | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	146
Agricultural land, production and other loans to farmers | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	226
Agricultural land, production and other loans to farmers | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	26	897
Construction
Financing Receivable, Past Due [Line Items]
Loans	521,889	484,723
Loans > 90 Days or More Past Due And Accruing	0	0
Construction | Current
Financing Receivable, Past Due [Line Items]
Loans	521,889	484,706
Construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	17
Construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Commercial real estate, non-owner occupied
Financing Receivable, Past Due [Line Items]
Loans	2,150,387	2,220,949
Loans > 90 Days or More Past Due And Accruing	0	0
Commercial real estate, non-owner occupied | Current
Financing Receivable, Past Due [Line Items]
Loans	2,142,055	2,184,681
Commercial real estate, non-owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	4,698	2,525
Commercial real estate, non-owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	424	2,109
Commercial real estate, non-owner occupied | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	3,210	31,634
Commercial real estate, owner occupied
Financing Receivable, Past Due [Line Items]
Loans	952,441	958,501
Loans > 90 Days or More Past Due And Accruing	0	0
Commercial real estate, owner occupied | Current
Financing Receivable, Past Due [Line Items]
Loans	950,676	951,561
Commercial real estate, owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	393	4,854
Commercial real estate, owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,017	180
Commercial real estate, owner occupied | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	355	1,906
Residential
Financing Receivable, Past Due [Line Items]
Loans	1,154,373	1,234,741
Loans > 90 Days or More Past Due And Accruing	111	133
Residential | Current
Financing Receivable, Past Due [Line Items]
Loans	1,147,965	1,226,779
Residential | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	2,982	3,269
Residential | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,195	1,429
Residential | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	2,231	3,264
Home equity
Financing Receivable, Past Due [Line Items]
Loans	531,307	508,259
Loans > 90 Days or More Past Due And Accruing	43	19
Home equity | Current
Financing Receivable, Past Due [Line Items]
Loans	528,760	503,596
Home equity | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	1,197	2,644
Home equity | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	355	559
Home equity | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	995	1,460
Individuals' loans for household and other personal expenditures
Financing Receivable, Past Due [Line Items]
Loans	135,093	129,479
Loans > 90 Days or More Past Due And Accruing	2	0
Individuals' loans for household and other personal expenditures | Current
Financing Receivable, Past Due [Line Items]
Loans	134,801	129,049
Individuals' loans for household and other personal expenditures | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	233	334
Individuals' loans for household and other personal expenditures | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	43	96
Individuals' loans for household and other personal expenditures | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	16	0
Public finance and other commercial loans
Financing Receivable, Past Due [Line Items]
Loans	781,785	647,939
Loans > 90 Days or More Past Due And Accruing	0	0
Public finance and other commercial loans | Current
Financing Receivable, Past Due [Line Items]
Loans	781,785	647,939
Public finance and other commercial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Public finance and other commercial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Loans	0	0
Public finance and other commercial loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Loans	$ 0	$ 0