| Document and Entity Information Document | Jul. 22, 2020 |
| DEI [Abstract] | |
| Entity Central Index Key | 0000875357 |
| Entity Incorporation, State or Country Code | OK |
| Document Type | 8-K |
| Document Period End Date | Jul. 22, 2020 |
| Entity File Number | 0-19341 |
| Entity Registrant Name | BOK FINANCIAL CORP ET AL |
| City Area Code | 918 |
| Local Phone Number | 588-6000 |
| 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 |
| Entity Address, Postal Zip Code | 74192 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
