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Loans - Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | $ 8,995.2 | $ 8,470.4
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3,465.8 | 3,235.4
Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 307.4 | 321.6
Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 261.0 | 242.8
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 353.4 | 274.3
Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 921.8 | 838.7
Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,559.1 | 1,542.0
Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 225.5 | 217.4
Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 6,172.2 | 5,833.5
Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 793.1 | 787.8
Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 201.7 | 200.6
Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,076.0 | 1,070.2
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,466.7 | 1,310.3
Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 277.6 | 254.8
Other Assets Especially Mentioned |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 182.5 | 178.8
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 94.0 | 102.5
Other Assets Especially Mentioned | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 5.2 | 5.0
Other Assets Especially Mentioned | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.8 | 2.8
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3.6 | 1.7
Other Assets Especially Mentioned | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 10.6 | 9.5
Other Assets Especially Mentioned | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.5 | 3.0
Other Assets Especially Mentioned | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 14.6 | 9.0
Other Assets Especially Mentioned | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 121.7 | 124.0
Other Assets Especially Mentioned | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.3 | 0.7
Other Assets Especially Mentioned | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.5 | 0.3
Other Assets Especially Mentioned | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.8 | 1.0
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 42.1 | 39.4
Other Assets Especially Mentioned | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 17.9 | 14.4
Substandard |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 217.0 | 201.6
Substandard | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 95.8 | 87.4
Substandard | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.8 | 7.0
Substandard | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.3 | 2.0
Substandard | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.6 | 3.9
Substandard | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 8.7 | 12.9
Substandard | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 7.2 | 10.8
Substandard | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 26.6 | 24.0
Substandard | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 138.3 | 135.1
Substandard | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.5 | 2.1
Substandard | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.0 | 0.8
Substandard | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3.5 | 2.9
Substandard | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 49.0 | 45.8
Substandard | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 26.2 | 17.8
Doubtful |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 14.5 | 20.9
Doubtful | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.0 | 2.9
Doubtful | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.1 | 3.3
Doubtful | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.4 | 0.4
Doubtful | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.0 | 0.0
Doubtful | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.5 | 3.7
Doubtful | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.5 | 0.7
Doubtful | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.3 | 0.1
Doubtful | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3.3 | 7.4
Doubtful | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.1 | 0.1
Doubtful | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.1 | 0.1
Doubtful | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.2 | 0.2
Doubtful | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 10.2 | 11.8
Doubtful | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.8 | 1.5
Total Criticized Loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 414.0 | 401.3
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 191.8 | 192.8
Total Criticized Loans | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 10.1 | 15.3
Total Criticized Loans | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.5 | 5.2
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 5.2 | 5.6
Total Criticized Loans | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 19.8 | 26.1
Total Criticized Loans | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 10.2 | 14.5
Total Criticized Loans | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 41.5 | 33.1
Total Criticized Loans | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 263.3 | 266.5
Total Criticized Loans | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.9 | 2.9
Total Criticized Loans | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.6 | 1.2
Total Criticized Loans | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.5 | 4.1
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 101.3 | 97.0
Total Criticized Loans | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | $ 44.9 | $ 33.7

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