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Loans Held for Investment and Allowance for Credit Losses on Loans - Summary of Energy Loans (Detail) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
--- | --- | ---
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | $ 6,191,230 | $ 6,394,506
Loans held for investment (net of unearned interest) | 6,191,230 | 6,394,506
Pegasus Bank [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 586,043 | 554,548
Loans held for investment (net of unearned interest) | 586,043 | 554,548
Energy [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 404,286 | 430,585
Loans held for investment (net of unearned interest) | 404,286 | 430,585
Energy [Member] | BancFirst’s [Member] | Upstream Energy Loans [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 141,651 | 190,788
Loans held for investment (net of unearned interest) | 141,651 | 190,788
Energy [Member] | BancFirst’s [Member] | Midstream Energy Loans [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 37,134 | 49,734
Loans held for investment (net of unearned interest) | 37,134 | 49,734
Energy [Member] | BancFirst’s [Member] | Ancillary Services [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 74,919 | 59,410
Loans held for investment (net of unearned interest) | 74,919 | 59,410
Energy [Member] | Pegasus Bank [Member] | Upstream Energy Loans [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 127,736 | 107,103
Loans held for investment (net of unearned interest) | 127,736 | 107,103
Energy [Member] | Pegasus Bank [Member] | Midstream Energy Loans [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 8,797 | 11,047
Loans held for investment (net of unearned interest) | 8,797 | 11,047
Energy [Member] | Pegasus Bank [Member] | Ancillary Services [Member] |  |
Financing Receivable Recorded Investment [Line Items] |  |
Total loans | 14,049 | 12,503
Loans held for investment (net of unearned interest) | $ 14,049 | $ 12,503

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- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524 + Details
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