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Employee Benefits (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
BOK Financial Pension Plan [Member] |  |  |
BOK Financial Pension Plan [Abstract] |  |  |
Interest percentage added to the five-year trailing average of five-year Treasury Securities | 1.50% |  |
Interest percentage accrued on employee account balances, Minimum | 3.00% |  |
Interest percentage accrued on employee account balances, Maximum | 5.00% |  |
Quarterly variable interest percentage accrued on employee account balances, minimum | 3.32% |  |
Quarterly variable interest percentage accrued on employee account balances, maximum | 3.40% |  |
Defined Benefit Plan, Benefit Obligation | $ 24,500,000 | $ 24,500,000 |
Defined Benefit Plan, Plan Assets, Amount | 36,400,000 | 33,600,000 |
Net periodic benefit cost (credit) | (815,000) | $ (583,000) | $ (704,000)
Total estimated future benefit payments | $ 27,800,000 |  |
BOK Financial Pension Plan Weighted-average Assumptions [Abstract] |  |  |
Discount rate (in hundredths) | 4.10% | 3.30% |
Expected return on plan assets (in hundredths) | 5.50% | 5.50% |
BOK Financial Pension Plan [Member] | Equity Securities [Member] |  |  |
BOK Financial Pension Plan [Abstract] |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 60.00% |  |
BOK Financial Pension Plan [Member] | Bonds [Member] |  |  |
BOK Financial Pension Plan [Abstract] |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage | 40.00% |  |
BOK Financial 401(k) Plan [Member] |  |  |
BOK Financial 401(k) Plan [Abstract] |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00% |  |
Defined Contribution Plan, Minimum Years of Service for Employees to Obtain Maximum Employer Matching | 4 years |  |
Defined Contribution Plan, Maximum Years of Service for Employees to Obtain Minimum Employer Matching | 15 years |  |
Contributions Non-Elective Annual Contributions For Qualified Employees | $ 750 |  |
Defined Contribution Plan, Annual Base Employee Compensation to Qualify for Non-Elective Employer Contributions, Maximum | $ 40,000 |  |
Defined Contribution Plan, Vesting Period for Employer Contributions | 5 years |  |
Defined Contribution Plan, Cost | $ 27,600,000 | $ 25,100,000 | $ 22,800,000
BOK Financial 401(k) Plan [Member] | Minimum [Member] |  |  |
BOK Financial 401(k) Plan [Abstract] |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 50.00% |  |
BOK Financial 401(k) Plan [Member] | Maximum [Member] |  |  |
BOK Financial 401(k) Plan [Abstract] |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 200.00% |  |

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- Definition The total amount of expected future benefit payments under a defined benefit plan. + References No definition available. + Details
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- Definition Defined Benefit Plan Interest Percentage Accrued on Employee Account Balances (Maximum) + References No definition available. + Details
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- Definition Represents the minimum interest rate used to accrued to employee account balances. + References No definition available. + Details
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- Definition Represents percentage added to five-year trailing average of five-year Treasury securities used in determining the interest accrued on employees' account balances. + References No definition available. + Details
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- Definition Represents the lower end of the range of variable interest rates used to accrued on employee account balances during the current year. + References No definition available. + Details
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- Definition The maximum annual base employee compensation to qualify for non-elective employer contributions under the deferred compensation plan. + References No definition available. + Details
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- Definition The minimum years of service for employees to obtain maximum employer matching under a defined contribution plan. + References No definition available. + Details
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