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Significant Accounting Policies Newly Adopted and Pending Accounting Pronouncements (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Increase of reported right of use assets and liabilities, minimum	$ 100
Increase of reported right of use assets and liabilities maximum	$ 150

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- Definition

Increase of reported right of use assets and liabilities minimum

+ References

No definition available.

+ Details

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- Definition

Increase of reported right of use assets and liabilities maximum

+ References

No definition available.

+ Details

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Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.

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