XML 46 R36.htm IDEA: XBRL DOCUMENT
v3.19.1

Trading Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Schedule of Trading Securities [Line Items] |  |
Trading securities | $ 2,140,326 | $ 1,956,923
Trading Securities, Net Unrealized Gain (Loss) | 12,898 | 10,969
U.S. government agency debentures [Member] |  |
Schedule of Trading Securities [Line Items] |  |
Trading securities | 51,576 | 63,765
Trading Securities, Net Unrealized Gain (Loss) | 52 | 254
Residential agency mortgage-backed securities [Member] |  |
Schedule of Trading Securities [Line Items] |  |
Trading securities | 1,952,742 | 1,791,584
Trading Securities, Net Unrealized Gain (Loss) | 12,377 | 9,966
Municipal and other tax-exempt securities [Member] |  |
Schedule of Trading Securities [Line Items] |  |
Trading securities | 50,637 | 34,507
Trading Securities, Net Unrealized Gain (Loss) | 225 | (1)
Asset-backed securities [Member] |  |
Schedule of Trading Securities [Line Items] |  |
Trading securities | 40,890 | 42,656
Trading Securities, Net Unrealized Gain (Loss) | 128 | 685
Other debt securities [Member] |  |
Schedule of Trading Securities [Line Items] |  |
Trading securities | 44,481 | 24,411
Trading Securities, Net Unrealized Gain (Loss) | $ 116 | $ 65

X
- Definition Represents the unrealized holding gain or loss included in the fair value of trading securities as of the balance sheet date. + References No definition available. + Details
Name: | bokf_TradingSecuritiesNetUnrealizedGainsLosses
Namespace Prefix: | bokf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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 No definition available. + Details
Name: | us-gaap_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 + Details
Name: | us-gaap_TradingSecuritiesDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesSecuritizedLoansAndReceivablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |