Related Parties Related Parties (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Directors and Senior Management [Member]
Loans and Leases Receivable, Related Parties [Roll Forward]
Beginning balance	$ 75,265	$ 110,246
Advances	886,610	1,479,735
Payments	(896,643)	(1,514,841)
Adjustments	9,957	125
Ending balance	75,189	75,265
Director [Member]
Loan Commitments and Equity Investments [Abstract]
Related Party Transaction, Expenses from Transactions with Related Party	$ 10,000
Executive Officer [Member]
Loan Commitments and Equity Investments [Abstract]
Percentage of investment funds' assets held by clients	84.00%
Assets Held in Cavanal Hill Funds	$ 3,700,000
Subsidiaries [Member] \| BOKF, NA [Member] \| Affiliated Entity [Member]
Loan Commitments and Equity Investments [Abstract]
Maximum percentage of unimpaired capital on loan commitments and equity investments to a single affiliate (in hundredths)	10.00%
Maximum percentage of unimpaired capital on loan commitments and equity investments to all affiliates (in hundredths)	20.00%
Maximum loan commitments and equity investments to a single affiliate	$ 370,000
Maximum loan commitments and equity investments to all affiliates	739,000
Largest loan commitment and equity investment to a single affiliate	257,000
Aggregate loan commitment and equity investment to all affiliates	392,000	313,000
Outstanding amounts to all affiliates	5,000	$ 883
Largest amount outstanding to a single affiliate	$ 4,300

The aggregate amount of largest loan commitment and equity investment to all affiliates.

No definition available.

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- Definition

The amount of assets held in investment funds.

+ References

No definition available.

+ Details

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- Definition

Largest amount outstanding to a single affiliate at balance sheet date

+ References

No definition available.

+ Details

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- Definition

The amount of largest loan commitment and equity investment to a single affiliate.

+ References

No definition available.

+ Details

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- Definition

Loan Commitments and Equity Investments [Abstract]

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

The amount of maximum loan commitments and equity investments to all affiliates.

+ References

No definition available.

+ Details

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- Definition

The amount of maximum loan commitments and equity investments to a single affiliate.

+ References

No definition available.

+ Details

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- Definition

The maximum percentage of unimpaired capital on loan commitments and equity investments to all affiliates.

+ References

No definition available.

+ Details

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- Definition

The maximum percentage of unimpaired capital on loan commitments and equity investments to a single affiliate.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- 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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

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

+ References

+ Details

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- Definition

Amount of cash inflow from related parties which reduce the amount of loans and leases receivable due from related parties.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7)(e)(1)(i))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(k)(1))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

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