Acquisition Acquisition	9 Months Ended
Sep. 30, 2018
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	On October 1, 2018, the Company acquired CoBiz Financial, Inc. (CoBiz). CoBiz is headquartered in Denver with a presence in Colorado and Arizona. The Company paid total consideration of $944 million, which included $242 million in cash along with the issuance of 7.2 million shares of BOK Financial stock valued at $702 million in exchange for all outstanding shares of CoBiz stock. As of September 30, 2018, CoBiz had $3.1 billion in loans, $3.9 billion in total assets, $3.3 billion in deposits and $339 million in equity. The assets and liabilities of CoBiz and the results of its operations will be consolidated for periods after the acquisition date. On May 1, 2018, the Company acquired a majority voting interest in Switchgrass Holdings, LLC, a restaurant franchise owner and operator, pursuant to merchant banking regulations and restrictions. The purchase price for this acquisition was $14 million. As of September 30, 2018, the preliminary purchase price allocation included $6.7 million of intangible assets.

Acquisition Acquisition

9 Months Ended

Sep. 30, 2018

Business Combination Disclosure [Text Block]

On October 1, 2018, the Company acquired CoBiz Financial, Inc. (CoBiz). CoBiz is headquartered in Denver with a presence in Colorado and Arizona. The Company paid total consideration of $944 million, which included $242 million in cash along with the issuance of 7.2 million shares of BOK Financial stock valued at $702 million in exchange for all outstanding shares of CoBiz stock. As of September 30, 2018, CoBiz had $3.1 billion in loans, $3.9 billion in total assets, $3.3 billion in deposits and $339 million in equity. The assets and liabilities of CoBiz and the results of its operations will be consolidated for periods after the acquisition date.

On May 1, 2018, the Company acquired a majority voting interest in Switchgrass Holdings, LLC, a restaurant franchise owner and operator, pursuant to merchant banking regulations and restrictions. The purchase price for this acquisition was $14 million. As of September 30, 2018, the preliminary purchase price allocation included $6.7 million of intangible assets.