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Loans Held for Investment - Schedule of Contractual Aging of Loans by Portfolio (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2022 | Sep. 30, 2021 | Dec. 31, 2021
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Nonaccrual loans | $ 43,100,000 |  | $ 43,100,000 |  |
Financing Receivable, Nonaccrual, Interest Income |  |  | 0 |  | $ 0
Impaired Financing Receivable, Interest Income, Accrual Method | 0 | $ 0 | 0 | $ 0 |
Accrued interest reversal |  |  | 600,000 |  |
Commercial real estate |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 13,800,000 |  | 13,800,000 |  | 2,700,000
Nonaccrual loans | 26,500,000 |  | 26,500,000 |  | 8,000,000.0
Land acquisition & development |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,200,000 |  | 1,200,000 |  | 200,000
Nonaccrual loans | 3,900,000 |  | 3,900,000 |  | 700,000
Residential construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 4,300,000 |  | 4,300,000 |  | 4,200,000
Nonaccrual loans | 0 |  | 0 |  | 0
Commercial construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6,800,000 |  | 6,800,000 |  | 0
Nonaccrual loans | 0 |  | 0 |  | 0
Total construction loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 12,300,000 |  | 12,300,000 |  | 4,400,000
Nonaccrual loans | 3,900,000 |  | 3,900,000 |  | 700,000
Residential |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 5,700,000 |  | 5,700,000 |  | 3,900,000
Nonaccrual loans | 6,400,000 |  | 6,400,000 |  | 2,900,000
Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,000,000.0 |  | 2,000,000.0 |  | 2,100,000
Nonaccrual loans | 15,600,000 |  | 15,600,000 |  | 4,900,000
Total real estate loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 33,800,000 |  | 33,800,000 |  | 13,100,000
Nonaccrual loans | 52,400,000 |  | 52,400,000 |  | 16,500,000
Indirect consumer |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7,500,000 |  | 7,500,000 |  | 6,900,000
Nonaccrual loans | 2,000,000.0 |  | 2,000,000.0 |  | 1,700,000
Direct and advance lines |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,000,000.0 |  | 1,000,000.0 |  | 800,000
Nonaccrual loans | 100,000 |  | 100,000 |  | 100,000
Credit card |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,500,000 |  | 1,500,000 |  | 1,300,000
Nonaccrual loans | 0 |  | 0 |  | 0
Total consumer loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 10,000,000.0 |  | 10,000,000.0 |  | 9,000,000.0
Nonaccrual loans | 2,100,000 |  | 2,100,000 |  | 1,800,000
Commercial |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 13,000,000.0 |  | 13,000,000.0 |  | 6,700,000
Nonaccrual loans | 11,700,000 |  | 11,700,000 |  | 5,000,000.0
Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,300,000 |  | 2,300,000 |  | 700,000
Nonaccrual loans | 13,200,000 |  | 13,200,000 |  | 1,600,000
Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
Nonaccrual loans | 0 |  | 0 |  | 0
Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 59,100,000 |  | 59,100,000 |  | 29,500,000
Nonaccrual loans | 79,400,000 |  | 79,400,000 |  | 24,900,000
30 to 59 Days Past Due | Commercial real estate |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 9,700,000 |  | 9,700,000 |  | 1,100,000
30 to 59 Days Past Due | Land acquisition & development |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 600,000 |  | 600,000 |  | 200,000
30 to 59 Days Past Due | Residential construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3,900,000 |  | 3,900,000 |  | 4,200,000
30 to 59 Days Past Due | Commercial construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6,800,000 |  | 6,800,000 |  | 0
30 to 59 Days Past Due | Total construction loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 11,300,000 |  | 11,300,000 |  | 4,400,000
30 to 59 Days Past Due | Residential |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,100,000 |  | 1,100,000 |  | 3,000,000.0
30 to 59 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,300,000 |  | 1,300,000 |  | 1,900,000
30 to 59 Days Past Due | Total real estate loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 23,400,000 |  | 23,400,000 |  | 10,400,000
30 to 59 Days Past Due | Indirect consumer |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6,000,000.0 |  | 6,000,000.0 |  | 5,100,000
30 to 59 Days Past Due | Direct and advance lines |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 700,000 |  | 700,000 |  | 500,000
30 to 59 Days Past Due | Credit card |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 600,000 |  | 600,000 |  | 600,000
30 to 59 Days Past Due | Total consumer loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7,300,000 |  | 7,300,000 |  | 6,200,000
30 to 59 Days Past Due | Commercial |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 9,500,000 |  | 9,500,000 |  | 4,900,000
30 to 59 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,100,000 |  | 2,100,000 |  | 700,000
30 to 59 Days Past Due | Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
30 to 59 Days Past Due | Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 42,300,000 |  | 42,300,000 |  | 22,200,000
60 to 89 Days Past Due | Commercial real estate |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,700,000 |  | 2,700,000 |  | 1,000,000.0
60 to 89 Days Past Due | Land acquisition & development |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 400,000 |  | 400,000 |  | 0
60 to 89 Days Past Due | Residential construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
60 to 89 Days Past Due | Commercial construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
60 to 89 Days Past Due | Total construction loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 400,000 |  | 400,000 |  | 0
60 to 89 Days Past Due | Residential |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3,400,000 |  | 3,400,000 |  | 800,000
60 to 89 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 200,000
60 to 89 Days Past Due | Total real estate loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6,500,000 |  | 6,500,000 |  | 2,000,000.0
60 to 89 Days Past Due | Indirect consumer |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,300,000 |  | 1,300,000 |  | 1,400,000
60 to 89 Days Past Due | Direct and advance lines |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 200,000 |  | 200,000 |  | 200,000
60 to 89 Days Past Due | Credit card |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 400,000 |  | 400,000 |  | 200,000
60 to 89 Days Past Due | Total consumer loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,900,000 |  | 1,900,000 |  | 1,800,000
60 to 89 Days Past Due | Commercial |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,700,000 |  | 1,700,000 |  | 700,000
60 to 89 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 100,000 |  | 100,000 |  | 0
60 to 89 Days Past Due | Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
60 to 89 Days Past Due | Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 10,200,000 |  | 10,200,000 |  | 4,500,000
Equal to or Greater than 90 Days Past Due | Commercial real estate |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,400,000 |  | 1,400,000 |  | 600,000
Equal to or Greater than 90 Days Past Due | Land acquisition & development |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 200,000 |  | 200,000 |  | 0
Equal to or Greater than 90 Days Past Due | Residential construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 400,000 |  | 400,000 |  | 0
Equal to or Greater than 90 Days Past Due | Commercial construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
Equal to or Greater than 90 Days Past Due | Total construction loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 600,000 |  | 600,000 |  | 0
Equal to or Greater than 90 Days Past Due | Residential |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,200,000 |  | 1,200,000 |  | 100,000
Equal to or Greater than 90 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 700,000 |  | 700,000 |  | 0
Equal to or Greater than 90 Days Past Due | Total real estate loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3,900,000 |  | 3,900,000 |  | 700,000
Equal to or Greater than 90 Days Past Due | Indirect consumer |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 200,000 |  | 200,000 |  | 400,000
Equal to or Greater than 90 Days Past Due | Direct and advance lines |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 100,000 |  | 100,000 |  | 100,000
Equal to or Greater than 90 Days Past Due | Credit card |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 500,000 |  | 500,000 |  | 500,000
Equal to or Greater than 90 Days Past Due | Total consumer loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 800,000 |  | 800,000 |  | 1,000,000.0
Equal to or Greater than 90 Days Past Due | Commercial |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,800,000 |  | 1,800,000 |  | 1,100,000
Equal to or Greater than 90 Days Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 100,000 |  | 100,000 |  | 0
Equal to or Greater than 90 Days Past Due | Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0 |  | 0 |  | 0
Equal to or Greater than 90 Days Past Due | Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6,600,000 |  | 6,600,000 |  | 2,800,000
Financial Asset, Not Past Due | Commercial real estate |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7,986,600,000 |  | 7,986,600,000 |  | 3,960,800,000
Financial Asset, Not Past Due | Land acquisition & development |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 388,100,000 |  | 388,100,000 |  | 246,900,000
Financial Asset, Not Past Due | Residential construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 497,100,000 |  | 497,100,000 |  | 257,800,000
Financial Asset, Not Past Due | Commercial construction |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1,121,600,000 |  | 1,121,600,000 |  | 498,000,000.0
Financial Asset, Not Past Due | Total construction loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,006,800,000 |  | 2,006,800,000 |  | 1,002,700,000
Financial Asset, Not Past Due | Residential |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,115,600,000 |  | 2,115,600,000 |  | 1,531,400,000
Financial Asset, Not Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 783,300,000 |  | 783,300,000 |  | 206,900,000
Financial Asset, Not Past Due | Total real estate loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 12,892,300,000 |  | 12,892,300,000 |  | 6,701,800,000
Financial Asset, Not Past Due | Indirect consumer |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 771,300,000 |  | 771,300,000 |  | 729,000,000.0
Financial Asset, Not Past Due | Direct and advance lines |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 153,900,000 |  | 153,900,000 |  | 128,300,000
Financial Asset, Not Past Due | Credit card |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 72,700,000 |  | 72,700,000 |  | 63,600,000
Financial Asset, Not Past Due | Total consumer loans |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 997,900,000 |  | 997,900,000 |  | 920,900,000
Financial Asset, Not Past Due | Commercial |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,941,400,000 |  | 2,941,400,000 |  | 1,463,800,000
Financial Asset, Not Past Due | Agricultural |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 642,700,000 |  | 642,700,000 |  | 201,600,000
Financial Asset, Not Past Due | Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3,800,000 |  | 3,800,000 |  | 1,500,000
Financial Asset, Not Past Due | Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | $ 17,478,100,000 |  | $ 17,478,100,000 |  | $ 9,289,600,000

X
- Definition Amount of writeoff of accrued interest on financing receivable recognized by reversing interest income. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 3D -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL120267969-210447 + Details
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- Definition Amount of undisbursed portion of financing receivable balance. Excludes financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5066-111524 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount of interest income on financing receivable on nonaccrual status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 16 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447 + Details
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