Fair Value Measurements Fair Value Measurement, Measured On Non-Recurring Basis, Signfiicant Unobservable Inputs, Quantitative Information (Details) - Fair Value, Nonrecurring [Member] - USD ($) $ in Thousands	Dec. 31, 2021		Dec. 31, 2020
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | BOK Financial Pension Plan [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Defined Benefit Plan, Plan Assets, Amount	$ 39,000		$ 38,000
Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	1,990		20,423
Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	808		801
Real estate and other repossessed assets [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	0		2,842
Real estate and other repossessed assets [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	1,706		18,188
Discounted Cash Flow [Member] | Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 3 [Member] | Management knowledge of Industry [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 1,990		20,423
Discounted Cash Flow [Member] | Real estate and other repossessed assets [Member] | Fair Value, Inputs, Level 3 [Member] | Management knowledge of Industry [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure			$ 2,842
Minimum [Member] | Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	16.00%	[1]	1.00%	[2]
Maximum [Member] | Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	97.00%	[1]	91.00%	[2]
Weighted Average [Member] | Fair Value, Nonaccruing Loans | Fair Value, Inputs, Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance	37.00%	[1]	23.00%	[2]

[1] Represents fair value as a percentage of the unpaid principal balance.

[2] Represents fair value as a percentage of the unpaid principal balance.