Loans and Allowance - Credit Quality of Loan Portfolio by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 8,459,310	$ 7,224,467
Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,109,879	1,726,664
Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	93,861	92,404
Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	787,568	545,729
Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	3,052,698	2,832,102
Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,143,217	966,421
Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	588,984	528,157
Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	135,989	99,788
Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	547,114	433,202
Commercial Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6,447,193	5,528,751
Commercial Pass | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,956,985	1,660,879
Commercial Pass | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	78,558	78,446
Commercial Pass | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	749,249	492,358
Commercial Pass | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,894,366	2,669,491
Commercial Pass | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	196,710	170,075
Commercial Pass | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	24,211	24,653
Commercial Pass | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Pass | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	547,114	432,849
Commercial Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	147,328	115,342
Commercial Special Mention | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	81,179	23,246
Commercial Special Mention | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	5,626	5,966
Commercial Special Mention | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,613	2,185
Commercial Special Mention | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	57,776	76,037
Commercial Special Mention | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	877	7,373
Commercial Special Mention | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	257	535
Commercial Special Mention | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Special Mention | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	190,358	161,929
Commercial Substandard | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	71,715	42,539
Commercial Substandard | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	9,677	7,992
Commercial Substandard | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,634	24,224
Commercial Substandard | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	98,575	84,288
Commercial Substandard | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	8,075	2,076
Commercial Substandard | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	682	457
Commercial Substandard | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Substandard | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	353
Commercial Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Doubtful | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial Loss | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,668,247	1,410,521
Consumer Performing | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Performing | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Performing | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	35,072	25,419
Consumer Performing | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,981	2,285
Consumer Performing | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	932,743	782,080
Consumer Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	562,507	500,996
Consumer Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	135,944	99,741
Consumer Performing | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Non Performing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6,184	7,924
Consumer Non Performing | Commercial and industrial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Non Performing | Agricultural production financing and other loans to farmers
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Consumer Non Performing | Construction
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	1,543
Consumer Non Performing | Commercial and farmland
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	1
Consumer Non Performing | Residential
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,812	4,817
Consumer Non Performing | Home equity
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,327	1,516
Consumer Non Performing | Individuals' loans for household and other personal expenditures
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	45	47
Consumer Non Performing | Public finance and other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 0	$ 0