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Fair Value Measurements - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
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 | 0
Level 2 Inputs [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Loans held for sale | $ 21,718,000 | 53,719,000
Level 2 Inputs [Member] | BancFirst [Member] |  |
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] |  |
Loans held for sale |  | $ 21,600,000

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- Definition Amount of non-financial assets (liabilities) measured at fair value on a recurring basis. + References No definition available. + 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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