Securities Part 5 (Details) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	$ 858,000	$ 4,824,000	$ 4,580,000	$ 9,423,000
Aggregate Unrealized Loss on Private Issue RMBS	36,000,000		36,000,000
Estimated Unemployment Rate, Next Twelve Months (in hundredths)	9.50%		9.50%
Estimated Unemployment Rate, Months 13-33 (in hundredths)	8.00%		8.00%
Estimated Unemployement Rate, Thereafter (in hundreths)	8.00%		8.00%
Estimated housing price depreciation, Next Twelve Months (in hundredths)	6.00%		6.00%		8.00%
Estimated housing price growth per year, Thereafter (in hundredths)	2.00%		2.00%		2.00%
Discount Rate Used To Estimate Cash Flow, Minimum (in hundredths)	2.00%		2.00%
Discount Rate Used To Estimate Cash Flow, Maximum (in hundredths)	6.25%		6.25%
Other-than Temporary Impairment Credit Losses Recognized in Earnings [Roll Forward]
Balance of credit-related OTTI recognized on available for sale debt securities at beginning of period	72,057,000	57,223,000	76,131,000	52,624,000
Additions for credit-related OTTI not previously recognized	135,000	37,000	248,000	37,000
Additions for increases in credit-related OTTI previously recognized when there is no intent to sell and no requirement to sell before recovery of amortized cost	723,000	4,787,000	4,332,000	9,386,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	0	0	(7,796,000)	0
Balance of credit-related OTTI recognized on available for sale debt securities, end of period	$ 72,915,000	$ 62,047,000	$ 72,915,000	$ 62,047,000

Gross unrealized losses for below investment grade private issue RMBS at a point in time.

No definition available.

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

- Definition

The maximum discount rate used to calculate cash flow on current expected yields for loans in the bank's portfolio.

+ References

No definition available.

+ Details

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

- Definition

The minimum discount rate used to calculate cash flow on current expected yields for loans in the bank's portfolio.

+ References

No definition available.

+ Details

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

- Definition

Estimated housing price depreciation over the next twelve months.

+ References

No definition available.

+ Details

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

- Definition

Estimated housing price depreciation per year after the next twelve months.

+ References

No definition available.

+ Details

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

- Definition

Estimated Unemployement Rate, 33 Months and Following

+ References

No definition available.

+ Details

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

- Definition

Estimated unemployment rate for months 13 through 24.

+ References

No definition available.

+ Details

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

- Definition

Estimated unemployment rate for the next 12 months.

+ References

No definition available.

+ Details

Name:	bokf_EstimatedUnemploymentRateNext12Months
Namespace Prefix:	bokf_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 18B

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 8

-Subparagraph (e)

-SubTopic 10

-Topic 320

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27340-111563

+ Details

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

- Definition

This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which no such other than temporary impairment (OTTI) was previously recognized.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 18B

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 8

-Subparagraph (b)

-SubTopic 10

-Topic 320

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27340-111563

+ Details

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

- Definition

The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 8

-SubTopic 10

-Topic 320

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27340-111563

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 18B

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 18B

-Subparagraph g

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Definition

This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security because of the sale of impaired securities during the period.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 18B

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Section 50

-Paragraph 8

-Subparagraph (c)

-SubTopic 10

-Topic 320

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27340-111563

+ Details

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

- Details

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

- Definition

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 16B

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 7

-Footnote 2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Details

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