Loans and Allowance - Past Due Aging of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Current	$ 9,170,399	$ 8,432,491
Total Past Due	72,775	26,819
Total	9,243,174	8,459,310
Past due 90+ days and still accruing		69
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	19,638	15,586
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	11,187	2,965
90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	41,950	8,268
Past due 90+ days and still accruing	746
Commercial and industrial loans
Financing Receivable, Past Due [Line Items]
Current	2,761,473	2,105,757
Total Past Due	15,226	4,122
Total	2,776,699	2,109,879
Past due 90+ days and still accruing		4
Commercial and industrial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	5,866	3,086
Commercial and industrial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	6,571	154
Commercial and industrial loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	2,789	882
Past due 90+ days and still accruing	594
Agricultural land, production and other loans to farmers
Financing Receivable, Past Due [Line Items]
Current	280,615	333,012
Total Past Due	1,269	1,160
Total	281,884	334,172
Past due 90+ days and still accruing		0
Agricultural land, production and other loans to farmers | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	146	46
Agricultural land, production and other loans to farmers | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	226	64
Agricultural land, production and other loans to farmers | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	897	1,050
Past due 90+ days and still accruing	0
Construction
Financing Receivable, Past Due [Line Items]
Current	484,706	785,936
Total Past Due	17	1,632
Total	484,723	787,568
Past due 90+ days and still accruing		0
Construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	1,632
Construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	17	0
Construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Past due 90+ days and still accruing	0
Commercial real estate, non-owner occupied
Financing Receivable, Past Due [Line Items]
Current	2,184,681	1,899,190
Total Past Due	36,268	3,502
Total	2,220,949	1,902,692
Past due 90+ days and still accruing		0
Commercial real estate, non-owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	2,525	1,348
Commercial real estate, non-owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	2,109	544
Commercial real estate, non-owner occupied | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	31,634	1,610
Past due 90+ days and still accruing	0
Commercial real estate, owner occupied
Financing Receivable, Past Due [Line Items]
Current	951,561	906,881
Total Past Due	6,940	2,814
Total	958,501	909,695
Past due 90+ days and still accruing		0
Commercial real estate, owner occupied | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	4,854	976
Commercial real estate, owner occupied | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	180	208
Commercial real estate, owner occupied | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	1,906	1,630
Past due 90+ days and still accruing	0
Residential
Financing Receivable, Past Due [Line Items]
Current	1,226,779	1,134,650
Total Past Due	7,962	8,567
Total	1,234,741	1,143,217
Past due 90+ days and still accruing		22
Residential | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	3,269	4,976
Residential | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	1,429	1,279
Residential | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	3,264	2,312
Past due 90+ days and still accruing	133
Home equity
Financing Receivable, Past Due [Line Items]
Current	503,596	584,506
Total Past Due	4,663	4,478
Total	508,259	588,984
Past due 90+ days and still accruing		42
Home equity | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	2,644	3,083
Home equity | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	559	611
Home equity | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	1,460	784
Past due 90+ days and still accruing	19
Construction
Financing Receivable, Past Due [Line Items]
Current	129,049	135,445
Total Past Due	430	544
Total	129,479	135,989
Past due 90+ days and still accruing		1
Construction | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	334	439
Construction | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	96	105
Construction | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Past due 90+ days and still accruing	0
Public finance and other commercial loans
Financing Receivable, Past Due [Line Items]
Current	647,939	547,114
Total Past Due	0	0
Total	647,939	547,114
Past due 90+ days and still accruing		0
Public finance and other commercial loans | 30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Public finance and other commercial loans | 60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	0
Public finance and other commercial loans | 90 Days or More Past Due
Financing Receivable, Past Due [Line Items]
Past Due	0	$ 0
Past due 90+ days and still accruing	$ 0