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Loans - Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) - USD ($) $ in Millions | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | $ 8,459.2 | $ 8,470.4
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3,255.8 | 3,235.4
Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 292.7 | 321.6
Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 233.1 | 242.8
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 312.1 | 274.3
Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 837.9 | 838.7
Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,529.5 | 1,542.0
Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 210.4 | 217.4
Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 5,833.6 | 5,833.5
Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 775.7 | 787.8
Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 194.1 | 200.6
Credit card |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 77.2 | 81.8
Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,047.0 | 1,070.2
Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1,342.1 | 1,310.3
Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 234.7 | 254.8
Other Assets Especially Mentioned |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 186.2 | 178.8
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 100.4 | 102.5
Other Assets Especially Mentioned | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 5.1 | 5.0
Other Assets Especially Mentioned | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.9 | 2.8
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.8 | 1.7
Other Assets Especially Mentioned | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 7.8 | 9.5
Other Assets Especially Mentioned | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.6 | 3.0
Other Assets Especially Mentioned | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 15.7 | 9.0
Other Assets Especially Mentioned | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 126.5 | 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 | 0.3 | 0.3
Other Assets Especially Mentioned | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.6 | 1.0
Other Assets Especially Mentioned | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 42.3 | 39.4
Other Assets Especially Mentioned | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 16.8 | 14.4
Substandard |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 194.6 | 201.6
Substandard | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 90.9 | 87.4
Substandard | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.2 | 7.0
Substandard | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.2 | 2.0
Substandard | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.1 | 3.9
Substandard | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 8.5 | 12.9
Substandard | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 8.9 | 10.8
Substandard | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 18.0 | 24.0
Substandard | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 126.3 | 135.1
Substandard | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.7 | 2.1
Substandard | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.8 | 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 | 46.5 | 45.8
Substandard | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 18.3 | 17.8
Doubtful |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 21.7 | 20.9
Doubtful | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 2.8 | 2.9
Doubtful | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3.4 | 3.3
Doubtful | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.9 | 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 | 4.3 | 3.7
Doubtful | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.9 | 0.7
Doubtful | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 0.1 | 0.1
Doubtful | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 9.1 | 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 | 11.3 | 11.8
Doubtful | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.1 | 1.5
Total Criticized Loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 402.5 | 401.3
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 194.1 | 192.8
Total Criticized Loans | Land acquisition & development |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 10.7 | 15.3
Total Criticized Loans | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.0 | 5.2
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 5.9 | 5.6
Total Criticized Loans | Total construction loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 20.6 | 26.1
Total Criticized Loans | Residential |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 13.4 | 14.5
Total Criticized Loans | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 33.8 | 33.1
Total Criticized Loans | Total real estate loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 261.9 | 266.5
Total Criticized Loans | Indirect consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 3.1 | 2.9
Total Criticized Loans | Direct consumer |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 1.2 | 1.2
Total Criticized Loans | Total consumer loans |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 4.3 | 4.1
Total Criticized Loans | Commercial |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | 100.1 | 97.0
Total Criticized Loans | Agricultural |  |
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items] |  |
Loans held for investment | $ 36.2 | $ 33.7

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