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Fair Value Measurements - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Transfer of securities between levels of fair value hierarchy |  | $ 0
Days from origination after which mortgage loans are sold | 30 days |
Amount of non-financial assets (liabilities) measured at fair value on a recurring basis | $ 0 | 0
Non-financial assets or liabilities for which no impairment was provided | 0 |
BancFirst [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Loans held for sale | $ 21,600,000 |
BancFirst Insurance Services, Inc. [Member] | Customer Related Intangibles [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Impairment of intangible assets |  | $ 353,000

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- Definition Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy. + References No definition available. + Details
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- Definition The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275 + Details
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- Definition Amount, before valuation allowance, of financing receivable classified as held-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -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://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 948 -SubTopic 310 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=120238483&loc=d3e48678-111004 + Details
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