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Fair Value Measurements - Fair Value Inputs, Quantitative Information (Details) - USD ($) | 6 Months Ended |
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Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Write downs on OREO properties | $ 0 | $ 0 |
Minimum | Market Approach Valuation Technique |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Discount Rate for Level 3 Fair Value Disclosure | 0.00% |  |
Maximum | Market Approach Valuation Technique |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Discount Rate for Assets HFS Level 3 Fair Value | 0.00% |  |
Discount Rate for OREO Level 3 Fair Value | 96.20% |  |
Weighted Average | Market Approach Valuation Technique |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Discount Rate for Assets HFS Level 3 Fair Value | 0.00% |  |
Discount Rate for OREO Level 3 Fair Value | 11.60% |  |
Discount Rate for Level 3 Fair Value Disclosure | 26.10% |  |
Carrying Amount |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Net loans held for investment | $ 7,708,400,000 |  | $ 7,542,200,000
Change During Period | Fair Value Measured on a Non-recurring Basis |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Fair Value of long-lived assets to be disposed of by sale | 500,000 |  | 0
Estimated Fair Value |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Net loans held for investment | 7,472,100,000 |  | 7,298,800,000
Estimated Fair Value | Fair Value Measured on a Non-recurring Basis |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Impaired loans | 36,000,000 |  | 32,600,000
Other real estate owned | 800,000 |  | 1,300,000
Fair Value of long-lived assets to be disposed of by sale | 3,500,000 |  | 800,000
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Impaired loans |  |  | 32,600,000
Other real estate owned | 800,000 |  | 1,300,000
Fair Value of long-lived assets to be disposed of by sale | 3,500,000 |  | 800,000
Significant Unobservable Inputs (Level 3) | Carrying Amount | Fair Value Measured on a Non-recurring Basis |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Impaired loans | 52,400,000 |  | 54,800,000
Fair Value of long-lived assets to be disposed of by sale | 4,000,000 |  | 800,000
Significant Unobservable Inputs (Level 3) | Estimated Fair Value |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Net loans held for investment |  |  | 32,600,000
Impaired loans | 36,000,000 |  |
Significant Unobservable Inputs (Level 3) | Estimated Fair Value | Fair Value Measured on a Non-recurring Basis |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Impaired loans | $ 36,000,000 |  | $ 32,600,000
Measurement Input, Discount Rate [Member] | Minimum | Market Approach Valuation Technique |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Discount Rate for Assets HFS Level 3 Fair Value | 0.00% |  |
Discount Rate for OREO Level 3 Fair Value | 8.00% |  |
Measurement Input, Discount Rate [Member] | Maximum | Market Approach Valuation Technique |  |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31) |  |  |
Discount Rate for Level 3 Fair Value Disclosure | 78.10% |  |

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- Definition Discount Rate for Impaired Loans Level 3 Fair Value + References No definition available. + Details
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- Definition Fair value portion of assets classified as held for sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19190-110258 + Details
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- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -URI http://asc.fasb.org/subtopic&trid=2196772 + Details
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