Mortgage Banking Activities Mortgage Banking Activities, Mortgage Banking Revenue (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Mortgage Banking Revenue [Abstract]
Net realized gains on mortgage loans	$ 17,251us-gaap_GainLossOnSaleOfMortgageLoans	$ 9,179us-gaap_GainLossOnSaleOfMortgageLoans
Net change in unrealized gain on mortgage loans held for sale	3,451	2,797
Change in fair value of mortgage loan commitments	7,529	3,379
Change in the fair value of forward sales contracts	(2,191)	(3,903)
Total production revenue	26,040bokf_MortgageProductionRevenue	11,452bokf_MortgageProductionRevenue
Servicing revenue	13,280us-gaap_ServicingFeesNet	11,392us-gaap_ServicingFeesNet
Total mortgage banking revenue	$ 39,320bokf_MortgageBankingRevenue	$ 22,844bokf_MortgageBankingRevenue

Represents the change in fair value of mortgage loan commitments during the period.

No definition available.

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

- Definition

Represents the change in the fair value of forward sales commitments considered to be derivative instruments during the period.

+ References

No definition available.

+ Details

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

- Definition

Noninterest income derived from the sale and changes in fair value of residential mortgage loans held for sale and fees for servicing of residential mortgage loans held by third parties. Also includes changes in the fair value of residential mortgage loan commitments and forward sales commitments considered to be derivative instruments.

+ References

No definition available.

+ Details

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

- Details

Name:	bokf_MortgageBankingRevenueAbstract
Namespace Prefix:	bokf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Total gain (loss) on mortgage loans held for sale, including mortgage loan commitments and forward sales contracts.

+ References

No definition available.

+ Details

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

- Definition

Represents the net change in unrealized gain on mortgage loans held for sale under fair value option.

+ References

No definition available.

+ Details

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

- Definition

The gains (losses) included in earnings that represent the difference between the sale price and the carrying value of loans made to finance real estate acquisitions. This element refers to the gain (loss) and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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

- Definition

Amount of revenue from servicing real estate mortgages, credit cards, and other financial assets held by others. Includes premiums received in lieu of regular servicing fees.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13 (d))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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