Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
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

Non financial assets liabilities for which no impairment provided.

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- Definition

Amount of non-financial assets (liabilities) measured at fair value on a recurring basis.

+ References

No definition available.

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- Definition

Period for sale of mortgage loan from origination.

+ References

No definition available.

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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.

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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.

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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

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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

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