Related Parties Related Parties (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable, Related Parties [Roll Forward]
Lease payments on office space in facilities owned by related party afffiliates	$ 25,000,000us-gaap_OperatingLeasesRentExpenseNet	$ 23,500,000us-gaap_OperatingLeasesRentExpenseNet	$ 21,700,000us-gaap_OperatingLeasesRentExpenseNet
Management [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance	88,691,000	49,943,000
Advances	712,413,000	292,393,000
Payments	(698,149,000)	(253,645,000)
Adjustments	440,000	0
Ending balance	103,395,000	88,691,000
Board of Directors Chairman [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Lease payments on office space in facilities owned by related party afffiliates	900,000	952,000	1,100,000
Executive Officer [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Loan commitment secured by tax-exempt bonds purchased from a trust of which the related party is chairman of the trust	25,000,000
Percentage of investment funds' assets held by clients	99.00%
Assets Held in Cavanal Hill Funds	$ 3,200,000,000

The amount of assets held in investment funds.

No definition available.

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

- Definition

Reflects the amount of adjustments made with related parties in the form of loans and lease receivables.

+ References

No definition available.

+ Details

Name:	bokf_LoansAndLeasesReceivableRelatedPartiesAdjustments
Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Outstanding commitments to extend credit based on existing credit policies.

+ References

No definition available.

+ Details

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

- Definition

The percentage of an investment fund's assets help by a company's clients.

+ References

No definition available.

+ Details

Name:	bokf_PercentageOfInvestmentFundsAssetsHeldForClients
Namespace Prefix:	bokf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(e))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph e

-Article 9

+ Details

Name:	us-gaap_LoansAndLeasesReceivableRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the amount of new advances made to related parties in the form of loan and lease receivables.

+ References

+ Details

Name:	us-gaap_LoansAndLeasesReceivableRelatedPartiesAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reflects the amount of collections received from related parties to reduce the carrying amounts of loans and leases receivable due from them.

+ References

+ Details

Name:	us-gaap_LoansAndLeasesReceivableRelatedPartiesCollections
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

+ Details

Name:	us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ManagementMember
Namespace Prefix:
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