Commitments and Contingent Liabilities Guarantor Obligations (Details) (USD $)	12 Months Ended
Dec. 31, 2014
Property Lease Guarantee [Member]
Guarantor Obligations [Line Items]
Total amount of guaranteed rents	$ 28,700,000
Contingent Obligation For Guaranteed Rents	8,400,000
Guaranteed Percentage To Be Received	80.00%
Maximum Amount To Be Received Under Rent Agreement With City Of Tulsa	4,500,000
BOSC, Inc. [Member]
Guarantor Obligations [Line Items]
Customer balances subject to indemnification by Pershing, LLC	$ 72,000

Customer balances subject to indemnification by Pershing, LLC

No definition available.

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Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Guaranteed percentage of cash flow to be received by company as per agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	bokf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future recourse payments the guarantor may receive under the guarantee or each group of similar guarantees as potential recoveries under recourse provisions.

+ References

No definition available.

+ Details

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Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total amount of guaranteed rents covered by the agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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- Details

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Period Type: