Significant Accounting Policies	3 Months Ended
Mar. 31, 2016
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	(1) Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements of BOK Financial Corporation (“BOK Financial” or “the Company”) have been prepared in accordance with accounting principles for interim financial information generally accepted in the United States and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. The unaudited consolidated financial statements include accounts of BOK Financial and its subsidiaries, principally BOKF, NA (“the Bank”), BOSC, Inc., The Milestone Group, Inc. and Cavanal Hill Investment Management Inc. Operating divisions of the Bank include Bank of Albuquerque, Bank of Arizona, Bank of Arkansas, Bank of Oklahoma, Bank of Texas, Colorado State Bank and Trust, Bank of Kansas City, BOK Financial Mortgage and the TransFund electronic funds network. Certain reclassifications have been made to conform to the current period presentation. The financial information should be read in conjunction with BOK Financial’s 2015 Form 10-K filed with the Securities and Exchange Commission, which contains audited financial statements. Amounts presented as of December 31, 2015 have been derived from the audited financial statements included in BOK Financial’s 2015 Form 10-K but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. Operating results for the three-month period ended March 31, 2016 are not necessarily indicative of the results that may be expected for the year ending December 31, 2016. Newly Adopted and Pending Accounting Policies Financial Accounting Standards Board (“FASB”) FASB Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers ("ASU 2014-09") On May 28, 2014, the FASB issued ASU 2014-09 to clarify the principles for recognizing revenue by providing a more robust framework that will give greater consistency and comparability in revenue recognition practices. In the new framework, an entity recognizes revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The new model requires the identification of performance obligations included in contracts with customers, a determination of the transaction price and an allocation of the price to those performance obligations. The entity recognizes revenue when performance obligations are satisfied. ASU 2014-09 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2014-09 will have on the Company's financial statements. FASB Accounting Standards Update No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share is More Akin to Debt or to Equity ("ASU 2014-16") On November 3, 2014, the FASB issued ASU 2014-16 to eliminate the use of different methods and reduce diversity under GAAP in the accounting for hybrid financial instruments issued in the form of a share. For hybrid financial instruments issued in the form of a share, an entity should determine the nature of the host contract by considering all stated and implied substantive terms and features of the hybrid financial instrument. The entity should determine the nature of the host contract by considering the economic characteristics and risks of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract. For public business entities, the ASU is effective for annual periods beginning after December 15, 2015, and interim periods within those annual periods. Adoption of ASU 2014-16 did not have a material impact on the Company's consolidated financial statements. FASB Accounting Standards Update No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis ("ASU 2015-02") On February 18, 2015, the FASB issued ASU 2015-02 to address concerns that current U.S. GAAP may require a reporting entity to consolidate another legal entity where the reporting entity's contractual rights do not give it the ability to act primarily on its own behalf, the reporting entity does not hold a majority of the legal entity's voting rights, or the reporting entity is not exposed to a majority of the legal entity's economic benefits or obligations. The amendments affect limited partnerships and similar legal entities, the evaluation of fees paid to a decision maker or a service provider as a variable interest, the effect of fee arrangements and related parties on the primary beneficiary determination, and certain investment funds. The ASU will be effective for periods beginning after December 15, 2015 for public companies. Adoption of ASU 2015-02 did not have a material impact on the Company's consolidated financial statements. FASB Accounting Standards Update No. 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) ("ASU 2015-07") On May 1, 2015, the FASB issued ASU 2015-07 to gain consistency within the categorization of the fair value hierarchy. The update removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. It also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. The ASU is effective for the Company for interim and annual periods beginning January 1, 2016 and should be applied retrospectively to all periods presented. Adoption of ASU 2015-07 did not have a material impact on the Company's consolidated financial statements. FASB Accounting Standards Update No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01") On January 5, 2016, the FASB issued ASU 2016-01 over the recognition and measurement of financial assets and liabilities. The update requires equity investments, in general, to be measured at fair value with changes in fair value recognized in earnings. It also eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires entities to use the exit price notion when measuring fair value, requires an entity to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from a change in the instrument-specific credit risk when the fair value option has been elected, requires separate presentation of financial assets and liabilities by measurement category and form on the balance sheet or accompanying notes, clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets, and simplifies the impairment assessment of equity investments without readily determinable fair values. The ASU is effective for the Company for interim and annual periods beginning after December 15, 2017. Upon adoption, unrealized gains and losses from equity securities will be reclassified from other comprehensive income to retained earnings. As of March 31, 2016, the Company had $2.0 million of unrealized gains and losses from equity securities in other comprehensive income. FASB Accounting Standards Update No. 2016-02, Leases (Topic 842) ("ASU 2016-02") On February 25, 2016, the FASB issued ASU 2016-02 to increase transparency and comparability by recognizing lease assets and liabilities on the balance and disclosing key information about leasing arrangements. The final guidance requires lessees to put most leases on their balance sheets and may affect the presentation and timing of expense recognition, eliminates the current real estate-specific provisions, modifies the classification criteria and the accounting for sales-type and direct financing leases for lessors. The ASU is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early application of the amendments is permitted. The Company is evaluating the impact the adoption of ASU 2016-02 will have on the Company's financial statements. FASB Accounting Standards Update No. 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships ("ASU 2016-05") On March 10, 2016, the FASB issued ASU 2016-05 which clarifies that "a change in the counterparty to a derivative instrument that has been designated as the hedging instrument in an existing hedging relationship would no, in and of itself, be considered a termination of the derivative instrument" or "a change in a critical term of the hedging relationship." If all other hedge accounting criteria in ASC 815 are met, a hedging relationship where the hedging derivative instrument is novated would not be discontinued or need to be redesignated. The ASU is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. An entity would apply the guidance prospectively unless modified retrospective transition is elected. Early adoption is permitted. The Company is evaluating the impact the adoption of ASU 2016-05 will have on the Company's financial statements. FASB Accounting Standards Update No. 2016-07, Investments - Equity Method and Joint Ventures ("ASU 2016-07") On March 15, 2016, the FASB issued ASU 2016-07 to simplify the equity method of accounting by eliminating the requirement to retrospectively apply the equity method to an investment that subsequently qualifies for such accounting as result of an increase in the level of ownership interest or degree of influence. The ASU also requires that unrealized holding gains or losses in accumulated other comprehensive income related to an available for sale security that becomes eligible for the equity method be recognized in earnings as of the date the investment qualifies for the equity method. The ASU is effective for all entities for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. Early adoption is permitted. The Company is evaluating the impact the adoption of ASU 2016-07 will have on the Company's financial statements. FASB Accounting Standards Update No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08") On March 17, 2016, the FASB Issued ASU 2016-08 to amend the principal versus agent implementation guidance in ASU 2014-09. The ASU clarifies that an entity should evaluate whether it is the principal or the agent for each specified good or service promised in a contract with a customer. ASU 2016-08 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2016-08 will have on the Company's financial statements along with ASU 2014-09. FASB Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09") On March 30, 2016, the FASB issued ASU 2016-09 to simplify multiple aspects of accounting for employee share-based payment transactions including accounting income taxes, forfeitures, and statutory tax withholding requirements. The ASU is effective for annual reporting periods beginning after December 15, 2016, including interim periods within those annual reporting periods. The Company is evaluating the impact the adoption of ASU 2016-09 will have on the Company's financial statements. FASB Accounting Standards Update No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing ("ASU 2016-10") On April 14, 2016, the FASB issued ASU 2016-10 which amends certain sections of ASU 2014-09 related to identifying performance obligations and licensing implementation. ASU 2016-10 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2016-10 will have on the Company's financial statements along with ASU 2014-09.

(1) Significant Accounting Policies

Basis of Presentation

The accompanying unaudited condensed consolidated financial statements of BOK Financial Corporation (“BOK Financial” or “the Company”) have been prepared in accordance with accounting principles for interim financial information generally accepted in the United States and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included.

The unaudited consolidated financial statements include accounts of BOK Financial and its subsidiaries, principally BOKF, NA (“the Bank”), BOSC, Inc., The Milestone Group, Inc. and Cavanal Hill Investment Management Inc. Operating divisions of the Bank include Bank of Albuquerque, Bank of Arizona, Bank of Arkansas, Bank of Oklahoma, Bank of Texas, Colorado State Bank and Trust, Bank of Kansas City, BOK Financial Mortgage and the TransFund electronic funds network.

Certain reclassifications have been made to conform to the current period presentation.

The financial information should be read in conjunction with BOK Financial’s 2015 Form 10-K filed with the Securities and Exchange Commission, which contains audited financial statements. Amounts presented as of December 31, 2015 have been derived from the audited financial statements included in BOK Financial’s 2015 Form 10-K but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. Operating results for the three-month period ended March 31, 2016 are not necessarily indicative of the results that may be expected for the year ending December 31, 2016.

Newly Adopted and Pending Accounting Policies

Financial Accounting Standards Board (“FASB”)

FASB Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers ("ASU 2014-09")

On May 28, 2014, the FASB issued ASU 2014-09 to clarify the principles for recognizing revenue by providing a more robust framework that will give greater consistency and comparability in revenue recognition practices. In the new framework, an entity recognizes revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The new model requires the identification of performance obligations included in contracts with customers, a determination of the transaction price and an allocation of the price to those performance obligations. The entity recognizes revenue when performance obligations are satisfied. ASU 2014-09 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2014-09 will have on the Company's financial statements.

FASB Accounting Standards Update No. 2014-16, Derivatives and Hedging (Topic 815): Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share is More Akin to Debt or to Equity ("ASU 2014-16")

On November 3, 2014, the FASB issued ASU 2014-16 to eliminate the use of different methods and reduce diversity under GAAP in the accounting for hybrid financial instruments issued in the form of a share. For hybrid financial instruments issued in the form of a share, an entity should determine the nature of the host contract by considering all stated and implied substantive terms and features of the hybrid financial instrument. The entity should determine the nature of the host contract by considering the economic characteristics and risks of the entire hybrid financial instrument, including the embedded derivative feature that is being evaluated for separate accounting from the host contract. For public business entities, the ASU is effective for annual periods beginning after December 15, 2015, and interim periods within those annual periods. Adoption of ASU 2014-16 did not have a material impact on the Company's consolidated financial statements.

FASB Accounting Standards Update No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis ("ASU 2015-02")

On February 18, 2015, the FASB issued ASU 2015-02 to address concerns that current U.S. GAAP may require a reporting entity to consolidate another legal entity where the reporting entity's contractual rights do not give it the ability to act primarily on its own behalf, the reporting entity does not hold a majority of the legal entity's voting rights, or the reporting entity is not exposed to a majority of the legal entity's economic benefits or obligations. The amendments affect limited partnerships and similar legal entities, the evaluation of fees paid to a decision maker or a service provider as a variable interest, the effect of fee arrangements and related parties on the primary beneficiary determination, and certain investment funds. The ASU will be effective for periods beginning after December 15, 2015 for public companies. Adoption of ASU 2015-02 did not have a material impact on the Company's consolidated financial statements.

FASB Accounting Standards Update No. 2015-07, Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) ("ASU 2015-07")

On May 1, 2015, the FASB issued ASU 2015-07 to gain consistency within the categorization of the fair value hierarchy. The update removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. It also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. The ASU is effective for the Company for interim and annual periods beginning January 1, 2016 and should be applied retrospectively to all periods presented. Adoption of ASU 2015-07 did not have a material impact on the Company's consolidated financial statements.

FASB Accounting Standards Update No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities ("ASU 2016-01")

On January 5, 2016, the FASB issued ASU 2016-01 over the recognition and measurement of financial assets and liabilities. The update requires equity investments, in general, to be measured at fair value with changes in fair value recognized in earnings. It also eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value for financial instruments measured at amortized cost, requires entities to use the exit price notion when measuring fair value, requires an entity to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from a change in the instrument-specific credit risk when the fair value option has been elected, requires separate presentation of financial assets and liabilities by measurement category and form on the balance sheet or accompanying notes, clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity's other deferred tax assets, and simplifies the impairment assessment of equity investments without readily determinable fair values. The ASU is effective for the Company for interim and annual periods beginning after December 15, 2017. Upon adoption, unrealized gains and losses from equity securities will be reclassified from other comprehensive income to retained earnings. As of March 31, 2016, the Company had $2.0 million of unrealized gains and losses from equity securities in other comprehensive income.

FASB Accounting Standards Update No. 2016-02, Leases (Topic 842) ("ASU 2016-02")

On February 25, 2016, the FASB issued ASU 2016-02 to increase transparency and comparability by recognizing lease assets and liabilities on the balance and disclosing key information about leasing arrangements. The final guidance requires lessees to put most leases on their balance sheets and may affect the presentation and timing of expense recognition, eliminates the current real estate-specific provisions, modifies the classification criteria and the accounting for sales-type and direct financing leases for lessors. The ASU is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020. Early application of the amendments is permitted. The Company is evaluating the impact the adoption of ASU 2016-02 will have on the Company's financial statements.

FASB Accounting Standards Update No. 2016-05, Derivatives and Hedging (Topic 815): Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships ("ASU 2016-05")

On March 10, 2016, the FASB issued ASU 2016-05 which clarifies that "a change in the counterparty to a derivative instrument that has been designated as the hedging instrument in an existing hedging relationship would no, in and of itself, be considered a termination of the derivative instrument" or "a change in a critical term of the hedging relationship." If all other hedge accounting criteria in ASC 815 are met, a hedging relationship where the hedging derivative instrument is novated would not be discontinued or need to be redesignated. The ASU is effective for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. An entity would apply the guidance prospectively unless modified retrospective transition is elected. Early adoption is permitted. The Company is evaluating the impact the adoption of ASU 2016-05 will have on the Company's financial statements.

FASB Accounting Standards Update No. 2016-07, Investments - Equity Method and Joint Ventures ("ASU 2016-07")

On March 15, 2016, the FASB issued ASU 2016-07 to simplify the equity method of accounting by eliminating the requirement to retrospectively apply the equity method to an investment that subsequently qualifies for such accounting as result of an increase in the level of ownership interest or degree of influence. The ASU also requires that unrealized holding gains or losses in accumulated other comprehensive income related to an available for sale security that becomes eligible for the equity method be recognized in earnings as of the date the investment qualifies for the equity method. The ASU is effective for all entities for fiscal years beginning after December 15, 2016, including interim periods within those fiscal years. Early adoption is permitted. The Company is evaluating the impact the adoption of ASU 2016-07 will have on the Company's financial statements.

FASB Accounting Standards Update No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) ("ASU 2016-08")

On March 17, 2016, the FASB Issued ASU 2016-08 to amend the principal versus agent implementation guidance in ASU 2014-09. The ASU clarifies that an entity should evaluate whether it is the principal or the agent for each specified good or service promised in a contract with a customer. ASU 2016-08 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2016-08 will have on the Company's financial statements along with ASU 2014-09.

FASB Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09")

On March 30, 2016, the FASB issued ASU 2016-09 to simplify multiple aspects of accounting for employee share-based payment transactions including accounting income taxes, forfeitures, and statutory tax withholding requirements. The ASU is effective for annual reporting periods beginning after December 15, 2016, including interim periods within those annual reporting periods. The Company is evaluating the impact the adoption of ASU 2016-09 will have on the Company's financial statements.

FASB Accounting Standards Update No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing ("ASU 2016-10")

On April 14, 2016, the FASB issued ASU 2016-10 which amends certain sections of ASU 2014-09 related to identifying performance obligations and licensing implementation. ASU 2016-10 is effective for the Company for annual reporting periods beginning after December 15, 2017, including interim periods within that reporting period. The Company is evaluating the impact the adoption of ASU 2016-10 will have on the Company's financial statements along with ASU 2014-09.