Loans and Allowances for Credit Losses, By Aging Category (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Financing receivable, recorded investment, aging [Abstract]
Current	$ 14,424,486	$ 13,933,715	$ 12,799,061
Past due 30 to 89 days	43,150	41,437	36,309
Past due 90 days or more	135,767	152,114	137,778
Nonaccrual	80,733	80,771	104,706
Total	14,684,136	14,208,037	13,077,854
Commercial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	9,369,363	9,078,724	8,027,248
Past due 30 to 89 days	7,842	3,419	5,411
Past due 90 days or more	78	0	0
Nonaccrual	13,880	13,527	19,047
Total	9,391,163	9,095,670	8,051,706
Energy [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,894,332	2,857,082	2,341,923
Past due 30 to 89 days	6,787	1,930	390
Past due 90 days or more	0	0	0
Nonaccrual	1,875	1,416	1,759
Total	2,902,994	2,860,428	2,344,072
Services [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,723,146	2,511,892	2,227,008
Past due 30 to 89 days	415	1,136	882
Past due 90 days or more	49	0	0
Nonaccrual	4,744	5,201	4,581
Total	2,728,354	2,518,229	2,232,471
Wholesale/retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,265,921	1,309,167	1,219,058
Past due 30 to 89 days	0	0	78
Past due 90 days or more	0	0	0
Nonaccrual	4,401	4,149	6,854
Total	1,270,322	1,313,316	1,225,990
Manufacturing [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	560,008	532,144	437,707
Past due 30 to 89 days	500	0	2,943
Past due 90 days or more	0	0	0
Nonaccrual	417	450	3,565
Total	560,925	532,594	444,215
Healthcare [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,509,594	1,453,409	1,394,479
Past due 30 to 89 days	25	180	640
Past due 90 days or more	0	0	0
Nonaccrual	1,558	1,380	1,443
Total	1,511,177	1,454,969	1,396,562
Other commercial and industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	416,362	415,030	407,073
Past due 30 to 89 days	115	173	478
Past due 90 days or more	29	0	0
Nonaccrual	885	931	845
Total	417,391	416,134	408,396
Commercial Real Estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	2,909,730	2,704,373	2,589,656
Past due 30 to 89 days	5,387	5,220	493
Past due 90 days or more	445	0	1,953
Nonaccrual	19,902	18,557	39,305
Total	2,935,464	2,728,150	2,631,407
Residential construction and land development [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	129,554	133,642	168,043
Past due 30 to 89 days	0	4,650	230
Past due 90 days or more	0	0	0
Nonaccrual	9,598	5,299	16,547
Total	139,152	143,591	184,820
Retail [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	654,558	662,963	634,497
Past due 30 to 89 days	0	0	0
Past due 90 days or more	445	0	1,383
Nonaccrual	3,857	3,926	4,626
Total	658,860	666,889	640,506
Office [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	511,452	412,124	429,700
Past due 30 to 89 days	0	0	263
Past due 90 days or more	0	0	0
Nonaccrual	2,410	3,420	6,301
Total	513,862	415,544	436,264
Multifamily [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	745,247	704,298	662,674
Past due 30 to 89 days	4,739	0	0
Past due 90 days or more	0	0	0
Nonaccrual	0	0	0
Total	749,986	704,298	662,674
Industrial [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	478,508	428,817	304,321
Past due 30 to 89 days	0	0	0
Past due 90 days or more	0	0	0
Nonaccrual	76	0	886
Total	478,584	428,817	305,207
Other commercial real estate [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	390,411	362,529	390,421
Past due 30 to 89 days	648	570	0
Past due 90 days or more	0	0	570
Nonaccrual	3,961	5,912	10,945
Total	395,020	369,011	401,936
Residential Mortgage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	1,715,775	1,717,028	1,807,639
Past due 30 to 89 days	29,493	32,251	29,832
Past due 90 days or more	135,244	152,112	135,824
Nonaccrual	46,487	48,121	45,380
Total	1,926,999	1,949,512	2,018,675
Permanent mortage [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	926,848	929,090	991,486
Past due 30 to 89 days	4,051	5,970	5,732
Past due 90 days or more	0	46	12
Nonaccrual	33,365	34,845	36,342
Total	964,264	969,951	1,033,572
Permanent mortgages guaranteed by US govenment agencies [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	39,309	26,691	26,919
Past due 30 to 89 days	22,370	23,558	20,544
Past due 90 days or more	135,244	151,989	135,787
Nonaccrual	3,256	3,712	1,572
Total	200,179	205,950	184,822
Home equity {Member]
Financing receivable, recorded investment, aging [Abstract]
Current	749,618	761,247	789,234
Past due 30 to 89 days	3,072	2,723	3,556
Past due 90 days or more	0	77	25
Nonaccrual	9,866	9,564	7,466
Total	762,556	773,611	800,281
Consumer [Member]
Financing receivable, recorded investment, aging [Abstract]
Current	429,618	433,590	374,518
Past due 30 to 89 days	428	547	573
Past due 90 days or more	0	2	1
Nonaccrual	464	566	974
Total	$ 430,510	$ 434,705	$ 376,066

Financing receivables that are less than 90 days past due but more than 29 days past due.

No definition available.

Name:	bokf_FinancingReceivableRecordedInvestment30To89DaysPastDue
Namespace Prefix:	bokf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Definition

Financing receivables that are current.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524

+ Details

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

- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524

+ Details

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

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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