Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim consolidated financial statements include the accounts of BancFirst Corporation, Council Oak Partners, LLC, BancFirst Insurance Services, Inc. and BancFirst and its subsidiaries. The principal operating subsidiaries of BancFirst are Council Oak Investment Corporation, Council Oak Real Estate, Inc. and BancFirst Agency, Inc. All significant intercompany accounts and transactions have been eliminated. Assets held in a fiduciary or agency capacity are not assets of the Company and, accordingly, are not included in the unaudited interim consolidated financial statements. The accompanying unaudited interim consolidated financial statements and notes are presented in accordance with the instructions for Form 10-Q. The information contained in the financial statements and footnotes included in BancFirst Corporation’s Annual Report on Form 10-K for the year ended December 31, 2016, should be referred to in connection with these unaudited interim consolidated financial statements. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for a full year or any future period. The unaudited interim consolidated financial statements contained herein reflect all adjustments which are, in the opinion of management, necessary to provide a fair statement of the financial position and results of operations of the Company for the interim periods presented. All such adjustments are of a normal and recurring nature. There have been no significant changes in the accounting policies of the Company since December 31, 2016, the date of the most recent annual report.
Use of Estimates in the Preparation of Financial Statements	Use of Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States inherently involves the use of estimates and assumptions that affect the amounts reported in the financial statements and the related disclosures. These estimates relate principally to the determination of the allowance for loan losses, income taxes, the fair value of financial instruments and the valuation of intangibles. Such estimates and assumptions may change over time and actual amounts realized may differ from those reported.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Standards Adopted During Current Period: In March 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2017-08, “Receivables – Nonrefundable Fees and Other Costs (Topic 310-20): Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. The Company opted for early adoption of ASU 2017-08, as was permitted, on January 1, 2017. ASU 2017-08 did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In October 2016, the FASB issued ASU No. 2016-17, “Consolidation (Topic 810): Interests Held Through Related Parties That Are Under Common Control.” ASU 2016-17 updates ASU No. 2015-02 to amend the consolidation guidance on how a reporting entity that is the single decision maker of a variable interest entity (“VIE”) should treat indirect interests in the entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of that VIE. ASU 2016-17 was adopted on January 1, 2017 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted. In March 2016, the FASB issued ASU No. 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” Under ASU 2016-09 all excess tax benefits and tax deficiencies related to share-based payment awards should be recognized as income tax expense or benefit in the income statement during the period in which they occur. Previously, such amounts were recorded in the pool of excess tax benefits included in additional paid-in capital, if such pool was available. Because excess tax benefits are no longer recognized in additional paid-in capital, the assumed proceeds from applying the treasury stock method when computing earnings per share should exclude the amount of excess tax benefits that would have previously been recognized in additional paid-in capital. Additionally, excess tax benefits should be classified along with other income tax cash flows as an operating activity rather than a financing activity, as was previously the case. ASU 2016-09 also allows entities to make an entity-wide accounting policy election to account for forfeitures when they occur, which the Company has elected to do. ASU 2016-09 changes the threshold to qualify for equity classification (rather than as a liability) to permit withholding up to the maximum statutory tax rates (rather than the minimum as was previously the case) in the applicable jurisdictions. ASU 2016-09 was adopted on January 1, 2017 and did not have a significant impact on the Company’s financial statements. In addition, ASU 2016-09 was applied prospectively and no prior periods were adjusted. The excess tax benefit for share-based payment awards that vested or were exercised during the three months ended March 31, 2017 was approximately $376,000. In August 2014, the FASB issued ASU No. 2014-15, “Presentation of Financial Statements – Going Concern (Topic 205-40).” ASU 2014-15 provides guidance on management’s responsibility in evaluating whether there is substantial doubt about the Company’s ability to continue as a going concern and related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date the financial statements are issued. ASU 2014-15 was adopted on January 1, 2017. Adoption of ASU 2014-15 did not have a significant effect on the Company’s financial statements. Standards Not Yet Adopted: In January 2017, the FASB issued ASU No. 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” ASU 2017-04 removes the second step of goodwill testing. ASU 2017-04 will be effective on January 1, 2020 and is not expected to have a significant impact on the Company’s financial statements. In January 2017, the FASB issued ASU No. 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of a business. ASU 2017-01 will be effective on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. In October 2016, the FASB issued ASU No. 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.” ASU 2016-16 provides guidance stating that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 will be effective on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements. In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 is intended to reduce the diversity in practice around how certain transactions are classified within the statement of cash flows. ASU 2016-15 will be effective on January 1, 2018. Early adoption is permitted with retrospective applications. The Company is currently evaluating the potential impact of ASU 2016-15 on its financial statements. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU 2016-13 requires enhanced disclosures related to the significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on its financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases - (Topic 842).” ASU 2016-02 requires that lessees recognize on the balance sheet the assets and liabilities for the rights and obligations created by leases. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2018. Early adoption is permitted. Adoption of ASU 2016-02 is not expected to have a significant effect on the Company’s financial statements. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments - Overall (Subtopic 825-10).” ASU 2016-01 require all equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in the fair value recognized through net income. In addition, the amendment will require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2017. Early adoption is not permitted. Adoption of ASU 2016-01 is not expected to have a significant effect on the Company’s financial statements. In January of 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customer (Topic 606).” ASU 2014-09 implements a comprehensive new revenue recognition standard that will supersede substantially all existing revenue recognition guidance. The new standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in a manner that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, which comprises a significant portion of the Company’s revenue stream. In August 2015, the FASB issued ASU No. 2015-14, “Revenue from Contracts with Customers (Topic 606).” ASU 2015-14 is an amendment to defer the effective date of ASU N. 2014-09. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2017. Adoption of ASU 2014-09 may require the Company to amend how it recognizes certain recurring revenue streams related to trust fees, which are recorded in non-interest expense; however, the Company does not expect the adoption of ASU 2014-09 to have a significant impact on the Company’s financial statements.

Recent Accounting Pronouncements

Standards Adopted During Current Period:

In March 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2017-08, “Receivables – Nonrefundable Fees and Other Costs (Topic 310-20): Premium Amortization on Purchased Callable Debt Securities.” ASU 2017-08 shortens the amortization period for certain callable debt securities held at a premium. The Company opted for early adoption of ASU 2017-08, as was permitted, on January 1, 2017. ASU 2017-08 did not have a significant impact on the Company’s financial statements and no prior periods were adjusted.

In October 2016, the FASB issued ASU No. 2016-17, “Consolidation (Topic 810): Interests Held Through Related Parties That Are Under Common Control.” ASU 2016-17 updates ASU No. 2015-02 to amend the consolidation guidance on how a reporting entity that is the single decision maker of a variable interest entity (“VIE”) should treat indirect interests in the entity held through related parties that are under common control with the reporting entity when determining whether it is the primary beneficiary of that VIE. ASU 2016-17 was adopted on January 1, 2017 and did not have a significant impact on the Company’s financial statements and no prior periods were adjusted.

In March 2016, the FASB issued ASU No. 2016-09, “Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” Under ASU 2016-09 all excess tax benefits and tax deficiencies related to share-based payment awards should be recognized as income tax expense or benefit in the income statement during the period in which they occur. Previously, such amounts were recorded in the pool of excess tax benefits included in additional paid-in capital, if such pool was available. Because excess tax benefits are no longer recognized in additional paid-in capital, the assumed proceeds from applying the treasury stock method when computing earnings per share should exclude the amount of excess tax benefits that would have previously been recognized in additional paid-in capital. Additionally, excess tax benefits should be classified along with other income tax cash flows as an operating activity rather than a financing activity, as was previously the case. ASU 2016-09 also allows entities to make an entity-wide accounting policy election to account for forfeitures when they occur, which the Company has elected to do. ASU 2016-09 changes the threshold to qualify for equity classification (rather than as a liability) to permit withholding up to the maximum statutory tax rates (rather than the minimum as was previously the case) in the applicable jurisdictions. ASU 2016-09 was adopted on January 1, 2017 and did not have a significant impact on the Company’s financial statements. In addition, ASU 2016-09 was applied prospectively and no prior periods were adjusted. The excess tax benefit for share-based payment awards that vested or were exercised during the three months ended March 31, 2017 was approximately $376,000.

In August 2014, the FASB issued ASU No. 2014-15, “Presentation of Financial Statements – Going Concern (Topic 205-40).” ASU 2014-15 provides guidance on management’s responsibility in evaluating whether there is substantial doubt about the Company’s ability to continue as a going concern and related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date the financial statements are issued. ASU 2014-15 was adopted on January 1, 2017. Adoption of ASU 2014-15 did not have a significant effect on the Company’s financial statements.

Standards Not Yet Adopted:

In January 2017, the FASB issued ASU No. 2017-04, “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” ASU 2017-04 removes the second step of goodwill testing. ASU 2017-04 will be effective on January 1, 2020 and is not expected to have a significant impact on the Company’s financial statements.

In January 2017, the FASB issued ASU No. 2017-01, “Business Combinations (Topic 805): Clarifying the Definition of a Business.” ASU 2017-01 clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of a business. ASU 2017-01 will be effective on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements.

In October 2016, the FASB issued ASU No. 2016-16, “Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory.” ASU 2016-16 provides guidance stating that an entity should recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. ASU 2016-16 will be effective on January 1, 2018 and is not expected to have a significant impact on the Company’s financial statements.

In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” ASU 2016-15 is intended to reduce the diversity in practice around how certain transactions are classified within the statement of cash flows. ASU 2016-15 will be effective on January 1, 2018. Early adoption is permitted with retrospective applications. The Company is currently evaluating the potential impact of ASU 2016-15 on its financial statements.

In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” ASU 2016-13 requires a financial asset measured at amortized cost basis to be presented at the net amount expected to be collected. The measurement of expected credit losses is based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. ASU 2016-13 requires enhanced disclosures related to the significant estimates and judgements used in estimating credit losses, as well as the credit quality and underwriting standards of an organization’s portfolio. In addition, ASU 2016-13 amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. ASU 2016-13 will be effective on January 1, 2020. The Company is currently evaluating the potential impact of ASU 2016-13 on its financial statements.

In February 2016, the FASB issued ASU No. 2016-02, “Leases - (Topic 842).” ASU 2016-02 requires that lessees recognize on the balance sheet the assets and liabilities for the rights and obligations created by leases. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2018. Early adoption is permitted. Adoption of ASU 2016-02 is not expected to have a significant effect on the Company’s financial statements.

In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments - Overall (Subtopic 825-10).” ASU 2016-01 require all equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in the fair value recognized through net income. In addition, the amendment will require an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2017. Early adoption is not permitted. Adoption of ASU 2016-01 is not expected to have a significant effect on the Company’s financial statements.

In January of 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customer (Topic 606).” ASU 2014-09 implements a comprehensive new revenue recognition standard that will supersede substantially all existing revenue recognition guidance. The new standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in a manner that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The guidance does not apply to revenue associated with financial instruments, including loans and securities that are accounted for under other GAAP, which comprises a significant portion of the Company’s revenue stream. In August 2015, the FASB issued ASU No. 2015-14, “Revenue from Contracts with Customers (Topic 606).” ASU 2015-14 is an amendment to defer the effective date of ASU N. 2014-09. The amendments are effective for annual periods, and interim reporting periods within those annual periods, beginning after December 15, 2017. Adoption of ASU 2014-09 may require the Company to amend how it recognizes certain recurring revenue streams related to trust fees, which are recorded in non-interest expense; however, the Company does not expect the adoption of ASU 2014-09 to have a significant impact on the Company’s financial statements.