Document And Entity Information	9 Months Ended
	Sep. 30, 2020 shares
Document and Entity Information [Abstract]
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1373454
Entity Address, Address Line One	Boston Avenue at Second Street
Entity Address, City or Town	Tulsa,
Entity Address, State or Province	OK
Document Transition Report	false
Document Quarterly Report	true
Entity Registrant Name	BOK FINANCIAL CORP
Entity Central Index Key	0000875357
Current Fiscal Year End Date	--12-31
Entity Emerging Growth Company	false
Entity Bankruptcy Proceedings, Reporting Current	false
Entity Small Business	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding	70,305,833
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Document Type	10-Q
Entity File Number	0-19341
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
City Area Code	918
Local Phone Number	588-6000
Entity Address, Postal Zip Code	74192