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Derivatives, Fair Value of Derivatives Contracts (Details) - USD ($) $ in Thousands | Sep. 30, 2019 | Dec. 31, 2018
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Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derviative contracts, net of cash collateral, Assets, Fair value | $ 352,019 |  | $ 320,929 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 336,791 |  | 362,306 |
Not Designated as Hedging Instrument [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 78,780,596 | [1] | 30,272,764 | [2]
Derivative Liabilities, Notional | 80,366,050 | [1] | 33,838,893 | [2]
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 675,084 |  | 571,793 |
Derivative Assets, Netting Adjustments | (255,979) |  | (135,530) |
Derivative Assets, Net Fair Value Before Cash Collateral | 419,105 |  | 436,263 |
Derivative Assets, Cash Collateral | (67,086) |  | (115,334) |
Derviative contracts, net of cash collateral, Assets, Fair value | 352,019 |  | 320,929 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 657,258 |  | 574,347 |
Derivative Liabilities, Netting Adjustments | (255,979) |  | (135,530) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 401,279 |  | 438,817 |
Derivative Liabilities, Cash Collateral | (64,488) |  | (76,511) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 336,791 |  | 362,306 |
Not Designated as Hedging Instrument [Member] | Total customer risk management programs |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 4,688,107 | [1] | 14,362,776 | [2]
Derivative Liabilities, Notional | 4,634,911 | [1] | 14,204,251 | [2]
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 460,859 |  | 521,383 |
Derivative Assets, Netting Adjustments | (59,681) |  | (94,659) |
Derivative Assets, Net Fair Value Before Cash Collateral | 401,178 |  | 426,724 |
Derivative Assets, Cash Collateral | (67,086) |  | (115,334) |
Derviative contracts, net of cash collateral, Assets, Fair value | 334,092 |  | 311,390 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 444,281 |  | 507,925 |
Derivative Liabilities, Netting Adjustments | (59,681) |  | (94,659) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 384,600 |  | 413,266 |
Derivative Liabilities, Cash Collateral | (62,780) |  | (69,196) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 321,820 |  | 344,070 |
Not Designated as Hedging Instrument [Member] | To-be-announced residential mortgage-backed securities [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 0 |  | 10,671,151 |
Derivative Liabilities, Notional | 0 |  | 10,558,151 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 0 |  | 92,231 |
Derivative Assets, Netting Adjustments | 0 |  | (26,787) |
Derivative Assets, Net Fair Value Before Cash Collateral | 0 |  | 65,444 |
Derivative Assets, Cash Collateral | 0 |  | 0 |
Derviative contracts, net of cash collateral, Assets, Fair value | 0 |  | 65,444 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 0 |  | 90,388 |
Derivative Liabilities, Netting Adjustments | 0 |  | (26,787) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 0 |  | 63,601 |
Derivative Liabilities, Cash Collateral | 0 |  | (63,596) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 0 |  | 5 |
Not Designated as Hedging Instrument [Member] | Interest rate swaps [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 2,399,788 |  | 1,924,131 |
Derivative Liabilities, Notional | 2,399,788 |  | 1,924,131 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 67,157 |  | 36,112 |
Derivative Assets, Netting Adjustments | (240) |  | (6,688) |
Derivative Assets, Net Fair Value Before Cash Collateral | 66,917 |  | 29,424 |
Derivative Assets, Cash Collateral | (277) |  | (7,934) |
Derviative contracts, net of cash collateral, Assets, Fair value | 66,640 |  | 21,490 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 67,296 |  | 36,288 |
Derivative Liabilities, Netting Adjustments | (240) |  | (6,688) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 67,056 |  | 29,600 |
Derivative Liabilities, Cash Collateral | (61,563) |  | (4,110) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 5,493 |  | 25,490 |
Not Designated as Hedging Instrument [Member] | Energy contracts [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 1,980,406 |  | 1,472,209 |
Derivative Liabilities, Notional | 1,936,369 |  | 1,434,247 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 183,204 |  | 206,418 |
Derivative Assets, Netting Adjustments | (59,139) |  | (60,983) |
Derivative Assets, Net Fair Value Before Cash Collateral | 124,065 |  | 145,435 |
Derivative Assets, Cash Collateral | (66,149) |  | (106,752) |
Derviative contracts, net of cash collateral, Assets, Fair value | 57,916 |  | 38,683 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 175,613 |  | 202,494 |
Derivative Liabilities, Netting Adjustments | (59,139) |  | (60,983) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 116,474 |  | 141,511 |
Derivative Liabilities, Cash Collateral | (784) |  | (1,490) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 115,690 |  | 140,021 |
Not Designated as Hedging Instrument [Member] | Agricultural contracts [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 15,538 |  | 21,210 |
Derivative Liabilities, Notional | 15,547 |  | 21,214 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 470 |  | 842 |
Derivative Assets, Netting Adjustments | (302) |  | (201) |
Derivative Assets, Net Fair Value Before Cash Collateral | 168 |  | 641 |
Derivative Assets, Cash Collateral | 0 |  | 0 |
Derviative contracts, net of cash collateral, Assets, Fair value | 168 |  | 641 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 451 |  | 812 |
Derivative Liabilities, Netting Adjustments | (302) |  | (201) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 149 |  | 611 |
Derivative Liabilities, Cash Collateral | 0 |  | 0 |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 149 |  | 611 |
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 209,515 |  | 184,990 |
Derivative Liabilities, Notional | 200,347 |  | 177,423 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 206,914 |  | 183,759 |
Derivative Assets, Netting Adjustments | 0 |  | 0 |
Derivative Assets, Net Fair Value Before Cash Collateral | 206,914 |  | 183,759 |
Derivative Assets, Cash Collateral | 0 |  | 0 |
Derviative contracts, net of cash collateral, Assets, Fair value | 206,914 |  | 183,759 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 197,807 |  | 175,922 |
Derivative Liabilities, Netting Adjustments | 0 |  | 0 |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 197,807 |  | 175,922 |
Derivative Liabilities, Cash Collateral | (433) |  | 0 |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 197,374 |  | 175,922 |
Not Designated as Hedging Instrument [Member] | Equity option contracts [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 82,860 |  | 89,085 |
Derivative Liabilities, Notional | 82,860 |  | 89,085 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 3,114 |  | 2,021 |
Derivative Assets, Netting Adjustments | 0 |  | 0 |
Derivative Assets, Net Fair Value Before Cash Collateral | 3,114 |  | 2,021 |
Derivative Assets, Cash Collateral | (660) |  | (648) |
Derviative contracts, net of cash collateral, Assets, Fair value | 2,454 |  | 1,373 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 3,114 |  | 2,021 |
Derivative Liabilities, Netting Adjustments | 0 |  | 0 |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 3,114 |  | 2,021 |
Derivative Liabilities, Cash Collateral | 0 |  | 0 |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 3,114 |  | 2,021 |
Not Designated as Hedging Instrument [Member] | Trading [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 73,658,685 |  | 15,356,909 |
Derivative Liabilities, Notional | 75,247,769 |  | 19,374,294 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 205,188 |  | 45,346 |
Derivative Assets, Netting Adjustments | (193,306) |  | (39,521) |
Derivative Assets, Net Fair Value Before Cash Collateral | 11,882 |  | 5,825 |
Derivative Assets, Cash Collateral | 0 |  | 0 |
Derviative contracts, net of cash collateral, Assets, Fair value | 11,882 |  | 5,825 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 207,542 |  | 56,983 |
Derivative Liabilities, Netting Adjustments | (193,306) |  | (39,521) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 14,236 |  | 17,462 |
Derivative Liabilities, Cash Collateral | 0 |  | 0 |
Derivative Liabilities, Fair Value, Net of Cash Collateral | 14,236 |  | 17,462 |
Not Designated as Hedging Instrument [Member] | Internal risk management programs [Member] |  |  |  |
Notional Amount of Derivatives [Abstract] |  |  |  |
Derivative Assets, Notional | 433,804 |  | 553,079 |
Derivative Liabilities, Notional | 483,370 |  | 260,348 |
Derivative Assets, Fair Value, Net [Abstract] |  |  |  |
Derivative Assets, Gross Fair Value | 9,037 |  | 5,064 |
Derivative Assets, Netting Adjustments | (2,992) |  | (1,350) |
Derivative Assets, Net Fair Value Before Cash Collateral | 6,045 |  | 3,714 |
Derivative Assets, Cash Collateral | 0 |  | 0 |
Derviative contracts, net of cash collateral, Assets, Fair value | 6,045 |  | 3,714 |
Derivative Liabilities, Fair Value, Net [Abstract] |  |  |  |
Derivative Liabilities, Gross Fair Value | 5,435 |  | 9,439 |
Derivative Liabilities, Netting Adjustments | (2,992) |  | (1,350) |
Derivative Liabilities, Net Fair Value Before Cash Collateral | 2,443 |  | 8,089 |
Derivative Liabilities, Cash Collateral | (1,708) |  | (7,315) |
Derivative Liabilities, Fair Value, Net of Cash Collateral | $ 735 |  | $ 774 |
[1] | Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.
[2] | Notional amounts for commodity contracts are converted into dollar-equivalent amounts based on dollar prices at the inception of the contract.

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Name: | us-gaap_DerivativeInstrumentRiskAxis=bokf_InternalRiskManagementProgramsMember
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Data Type: | na
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