Significant Accounting Policies	3 Months Ended
Mar. 31, 2015
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 2014 Form 10-K filed with the Securities and Exchange Commission, which contains audited financial statements. Amounts presented as of December 31, 2014 have been derived from the audited financial statements included in BOK Financial’s 2014 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, 2015 are not necessarily indicative of the results that may be expected for the year ending December 31, 2015. Newly Adopted and Pending Accounting Policies Financial Accounting Standards Board (“FASB”) FASB Accounting Standards Update No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("ASU 2014-01") On January 15, 2014, the FASB issued ASU 2014-01 to simplify the amortization method an entity uses and modify the criteria to elect a measurement and presentation alternative, including the simplified amortization method, for certain investments in qualified affordable housing projects. This alternative permits the entity to present the investment's performance net of the related tax benefits as part of income tax expense. ASU 2014-01 was effective for the Company for interim and annual periods beginning after December 15, 2014. Adoption of ASU 2014-01 affected income statement presentation, but otherwise did not have a material impact on the Company's consolidated financial statements. FASB Accounting Standards Update No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure ("ASU 2014-04") On January 17, 2014, the FASB issued ASU 2014-04 to clarify when an entity is considered to have obtained physical possession (from an in-substance possession or foreclosure) of a residential real estate property collateralizing a mortgage loan. Upon physical possession of such real property, an entity is required to reclassify the nonperforming mortgage loan to other real estate owned. ASU 2014-04 was effective for the Company for interim and annual periods beginning after December 15, 2014. Adoption of ASU 2014-04 did not have a material impact on the Company's consolidated financial statements. 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, 2016, 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. 2014-14, Classification of Certain Government-Guaranteed Mortgage Loans Upon Foreclosure ("ASU 2014-14") On August 8, 2014, the FASB issued ASU 2014-14 to give greater consistency in the classification of government-guaranteed loans upon foreclosure. ASU 2014-14 applies to all loans that contain a government guarantee that is not separable from the loan or for which the creditor has both the intent and ability to recover a fixed amount under the guarantee by conveying the property to the guarantor. Upon foreclosure, the creditor should reclassify the mortgage loan to an other receivable that is separate from loans and should measure the receivable at the amount of the loan balance expected to be recovered from the guarantor. ASU 2014-14 was effective for the Company for interim and annual periods beginning after December 15, 2014. At January 1, 2015, approximately $50 million of real estate owned was reclassified from Real estate and other repossessed assets to Receivables on the balance sheet with adoption of ASC 2014-14. 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 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. Early adoption is permitted. Adoption of ASU 2014-16 is not expected to 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. Early adoption is permitted, including adoption in an interim period. The Company is evaluating the impact the adoption of ASU 2015-02 will have on the Company's financial statements.

(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 2014 Form 10-K filed with the Securities and Exchange Commission, which contains audited financial statements. Amounts presented as of December 31, 2014 have been derived from the audited financial statements included in BOK Financial’s 2014 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, 2015 are not necessarily indicative of the results that may be expected for the year ending December 31, 2015.

Newly Adopted and Pending Accounting Policies

Financial Accounting Standards Board (“FASB”)

FASB Accounting Standards Update No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects ("ASU 2014-01")

On January 15, 2014, the FASB issued ASU 2014-01 to simplify the amortization method an entity uses and modify the criteria to elect a measurement and presentation alternative, including the simplified amortization method, for certain investments in qualified affordable housing projects. This alternative permits the entity to present the investment's performance net of the related tax benefits as part of income tax expense. ASU 2014-01 was effective for the Company for interim and annual periods beginning after December 15, 2014. Adoption of ASU 2014-01 affected income statement presentation, but otherwise did not have a material impact on the Company's consolidated financial statements.

FASB Accounting Standards Update No. 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure ("ASU 2014-04")

On January 17, 2014, the FASB issued ASU 2014-04 to clarify when an entity is considered to have obtained physical possession (from an in-substance possession or foreclosure) of a residential real estate property collateralizing a mortgage loan. Upon physical possession of such real property, an entity is required to reclassify the nonperforming mortgage loan to other real estate owned. ASU 2014-04 was effective for the Company for interim and annual periods beginning after December 15, 2014. Adoption of ASU 2014-04 did not have a material impact on the Company's consolidated financial statements.

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, 2016, 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. 2014-14, Classification of Certain Government-Guaranteed Mortgage Loans Upon Foreclosure ("ASU 2014-14")

On August 8, 2014, the FASB issued ASU 2014-14 to give greater consistency in the classification of government-guaranteed loans upon foreclosure. ASU 2014-14 applies to all loans that contain a government guarantee that is not separable from the loan or for which the creditor has both the intent and ability to recover a fixed amount under the guarantee by conveying the property to the guarantor. Upon foreclosure, the creditor should reclassify the mortgage loan to an other receivable that is separate from loans and should measure the receivable at the amount of the loan balance expected to be recovered from the guarantor. ASU 2014-14 was effective for the Company for interim and annual periods beginning after December 15, 2014. At January 1, 2015, approximately $50 million of real estate owned was reclassified from Real estate and other repossessed assets to Receivables on the balance sheet with adoption of ASC 2014-14.

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 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. Early adoption is permitted. Adoption of ASU 2014-16 is not expected to 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. Early adoption is permitted, including adoption in an interim period. The Company is evaluating the impact the adoption of ASU 2015-02 will have on the Company's financial statements.