Loans and Allowances for Credit Losses Loans and Allowances for Credit Losses, Nonaccrual (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	$ 72,394	$ 46,725
Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	72,394	46,725
Financing Receivable, Nonaccrual, No Allowance	54,685	46,449
Financing Receivable, Nonaccrual, With Allowance	17,709	276
Financing Receivable, Nonaccrual, Related Allowance	4,345	276
Commercial [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	32,270	14,647
Commercial [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	32,270	14,647
Financing Receivable, Nonaccrual, No Allowance	21,370	14,371
Financing Receivable, Nonaccrual, With Allowance	10,900	276
Financing Receivable, Nonaccrual, Related Allowance	2,150	276
Commercial [Member] \| Healthcare [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	24,507	13,717
Financing Receivable, Nonaccrual, No Allowance	19,405	13,717
Financing Receivable, Nonaccrual, With Allowance	5,102	0
Financing Receivable, Nonaccrual, Related Allowance	200	0
Commercial [Member] \| Services [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	7,647	767
Financing Receivable, Nonaccrual, No Allowance	1,849	491
Financing Receivable, Nonaccrual, With Allowance	5,798	276
Financing Receivable, Nonaccrual, Related Allowance	1,950	276
Commercial [Member] \| Energy [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	31	49
Financing Receivable, Nonaccrual, No Allowance	31	49
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Commercial [Member] \| General business [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	85	114
Financing Receivable, Nonaccrual, No Allowance	85	114
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Commercial real estate [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	6,809	9,905
Commercial real estate [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	6,809	9,905
Financing Receivable, Nonaccrual, No Allowance	0	9,905
Financing Receivable, Nonaccrual, With Allowance	6,809	0
Financing Receivable, Nonaccrual, Related Allowance	2,195	0
Loans to individuals [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	33,315	22,173
Loans to individuals [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	33,315	22,173
Financing Receivable, Nonaccrual, No Allowance	33,315	22,173
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Loans to individuals [Member] \| Residential mortgage [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	21,255	15,261
Financing Receivable, Nonaccrual, No Allowance	21,255	15,261
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
Loans to individuals [Member] \| Personal [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	4,712	109
Financing Receivable, Nonaccrual, No Allowance	4,712	109
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	0	0
US Government Agency Insured Loans [Member] \| Loans to individuals [Member] \| Residential mortgage [Member] \| Nonperforming Financial Instruments [Member] \| Nonaccrual [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual	7,348	6,803
Financing Receivable, Nonaccrual, No Allowance	7,348	6,803
Financing Receivable, Nonaccrual, With Allowance	0	0
Financing Receivable, Nonaccrual, Related Allowance	$ 0	$ 0

Amount of financing receivable on nonaccrual status with a related allowance.

No definition available.

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

- Definition

Amount of financing receivable on nonaccrual status with an allowance.

+ References

No definition available.

+ Details

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

- Definition

Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (d)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (d)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (b)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-12

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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

- Definition

Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (3)
-Publisher SEC

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph a
-Subparagraph (2)
-Publisher SEC

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=bokf_NonaccruingsubstandardanddoubtfulMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HealthCareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bokf_ServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bokf_EnergyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bokf_GeneralbusinessmemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=bokf_LoanstoindividualsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis=us-gaap_UsGovernmentAgencyInsuredLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: