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FDIC-Acquired Loans and Loss Sharing Agreements - Accretable Yield Changes for Acquired Loans (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
TeamBank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Beginning Balance |  | $ 1,157,000 | $ 1,356,000 | $ 2,071,000
Accretion |  | (479,000) | (955,000) | (1,042,000)
Reclassification from nonaccretable difference | [1] | 198,000 | 756,000 | 327,000
Ending balance |  | 876,000 | 1,157,000 | 1,356,000
Change in expected accretable yield |  | 198,000 | 667,000 | 312,000
Vantus Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Beginning Balance |  | 1,123,000 | 1,432,000 | 1,850,000
Accretion |  | (831,000) | (1,006,000) | (1,196,000)
Reclassification from nonaccretable difference | [1] | 451,000 | 697,000 | 778,000
Ending balance |  | 743,000 | 1,123,000 | 1,432,000
Change in expected accretable yield |  | 451,000 | 480,000 | 778,000
Sun Security Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Beginning Balance |  | 1,948,000 | 2,242,000 | 2,901,000
Accretion |  | (1,046,000) | (1,562,000) | (1,667,000)
Reclassification from nonaccretable difference | [1] | 493,000 | 1,268,000 | 1,008,000
Ending balance |  | 1,395,000 | 1,948,000 | 2,242,000
Change in expected accretable yield |  | 493,000 | 810,000 | 756,000
InterBank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Beginning Balance |  | 8,277,000 | 4,994,000 | 5,074,000
Accretion |  | (6,791,000) | (8,798,000) | (8,349,000)
Reclassification from nonaccretable difference | [1] | 2,219,000 | 12,081,000 | 8,269,000
Ending balance |  | 3,705,000 | 8,277,000 | 4,994,000
Change in expected accretable yield |  | 2,200,000 | 3,900,000 | 4,100,000
Valley Bank |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Beginning Balance |  | 4,578,000 | 3,063,000 | 2,695,000
Accretion |  | (3,005,000) | (4,302,000) | (3,892,000)
Reclassification from nonaccretable difference | [1] | 2,764,000 | 5,817,000 | 4,260,000
Ending balance |  | 4,337,000 | 4,578,000 | 3,063,000
Change in expected accretable yield |  | $ 2,800,000 | $ 2,500,000 | $ 3,500,000
[1] | Represents increases in estimated cash flows expected to be received from the acquired loan pools, primarily due to lower estimated credit losses. The numbers also include changes in expected accretion of the loan pools for TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2020, totaling $198,000, $451,000, $493,000, $2.2 million and $2.8 million, respectively; TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2019, totaling $667,000, $480,000, $810,000, $3.9 million and $2.5 million, respectively; for TeamBank, Vantus Bank, Sun Security Bank, InterBank and Valley Bank for the year ended December 31, 2018, totaling $312,000, $778,000, $756,000, $4.1 million and $3.5 million, respectively

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- Definition Amount of increase (decrease) of the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality. + References No definition available. + Details
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- Definition Represents the monetary amount of Change in expected accretable yield, during the indicated time period. + References No definition available. + Details
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- Definition Change in the estimate of cash flows expected to be collected, after acquisition of a loan, which results in an increase in accretable yield (for example, if actual cash flows are significantly greater than previously expected). This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121585399&loc=d3e13503-111538 + Details
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- Definition Amount of accretion recognized for the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities, with evidence of deterioration of credit quality. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121585399&loc=d3e13503-111538 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544 + Details
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