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Shareholders' Equity Regulatory Capital (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Common Equity Tier 1 Capital [Abstract] |  |  |
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets |  | 4.50% | 4.50%
Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets | [1] | 2.50% | 2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets |  | 7.00% | 7.00%
Common Equity Tier 1 Capital |  | $ 3,608,821 | $ 3,356,524
Common Equity Tier 1 Capital to Risk Weighted Assets |  | 11.39% | 10.92%
Tier I Capital (to Risk Weighted Assets) [Abstract] |  |  |
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets |  | 6.00% | 6.00%
Capital Conservation Buffer, Tier 1 Capital to Risk Weighted Assets | [1] | 2.50% | 2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets |  | 8.50% | 8.50%
Tier 1 Capital |  | $ 3,608,821 | $ 3,356,524
Tier 1 Capital to Risk Weighted Assets |  | 11.39% | 10.92%
Total Capital (to Risk Weighted Assets) [Abstract] |  |  |
Minimum Capital Requirement, Total Capital to Risk Weighted Assets |  | 8.00% | 8.00%
Capital Conservation Buffer, Total Capital to Risk Weighted Assets | [1] | 2.50% | 2.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets |  | 10.50% | 10.50%
Total Capital |  | $ 4,097,087 | $ 3,841,684
Total Capital to Risk Weighted Assets |  | 12.94% | 12.50%
Tier 1 Capital (to Average Assets) [Abstract] |  |  |
Minimum Capital Requirement, Tier 1 Capital to Average Assets |  | 4.00% | 4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets |  | 4.00% | 4.00%
Tier 1 Leverage Capital |  | $ 3,608,820 | $ 3,356,524
Tier 1 Capital to Average Assets |  | 8.40% | 8.96%
Phased in Capital Conservation Buffer |  | 2.50% | 1.875%
Fully Phased In Capital Conservation Buffer |  | 2.50% |
Subsidiaries [Member] | BOKF, NA [Member] |  |  |
Common Equity Tier 1 Capital [Abstract] |  |  |
Common Equity Tier 1 Capital Ratio Required to be Well Capitalized |  | 6.50% | 6.50%
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets |  | 4.50% | 4.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets |  | 4.50% | 4.50%
Common Equity Tier 1 Capital |  | $ 3,414,446 | $ 2,894,119
Common Equity Tier 1 Capital to Risk Weighted Assets |  | 10.90% | 10.50%
Tier I Capital (to Risk Weighted Assets) [Abstract] |  |  |
Tier I Capital Ratio Required to be Well Capitalized |  | 8.00% | 8.00%
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets |  | 6.00% | 6.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets |  | 6.00% | 6.00%
Tier 1 Capital |  | $ 3,414,446 | $ 2,894,119
Tier 1 Capital to Risk Weighted Assets |  | 10.90% | 10.50%
Total Capital (to Risk Weighted Assets) [Abstract] |  |  |
Total Capital Ratio Required to be Well Capitalized |  | 10.00% | 10.00%
Minimum Capital Requirement, Total Capital to Risk Weighted Assets |  | 8.00% | 8.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets |  | 8.00% | 8.00%
Total Capital |  | $ 3,692,010 | $ 3,103,366
Total Capital to Risk Weighted Assets |  | 11.79% | 11.26%
Tier 1 Capital (to Average Assets) [Abstract] |  |  |
Leverage Ratio Required to be Well Capitalized |  | 5.00% | 5.00%
Minimum Capital Requirement, Tier 1 Capital to Average Assets |  | 4.00% | 4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets |  | 4.00% | 4.00%
Tier 1 Leverage Capital |  | $ 3,414,446 | $ 2,894,119
Tier 1 Capital to Average Assets |  | 7.98% | 8.56%
Subsidiaries [Member] | CoBiz Bank [Member] |  |  |
Common Equity Tier 1 Capital [Abstract] |  |  |
Common Equity Tier 1 Capital Ratio Required to be Well Capitalized | [2] | 6.50% | 6.50%
Minimum Capital Requirements, Common Equity Tier 1 to Risk Weighted Assets | [2] | 4.50% | 4.50%
Minimum Capital Requirement Including Capital Conservation Buffer, Common Equity Tier 1 to Risk Weighted Assets | [2] | 4.50% | 4.50%
Common Equity Tier 1 Capital | [2] | $ 0 | $ 317,944
Common Equity Tier 1 Capital to Risk Weighted Assets | [2] | 0.00% | 10.65%
Tier I Capital (to Risk Weighted Assets) [Abstract] |  |  |
Tier I Capital Ratio Required to be Well Capitalized | [2] | 8.00% | 8.00%
Minimum Capital Requirement, Tier 1 Capital to Risk Weighted Assets | [2] | 6.00% | 6.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Tier One to Risk Weighted Assets | [2] | 6.00% | 6.00%
Tier 1 Capital | [2] | $ 0 | $ 317,944
Tier 1 Capital to Risk Weighted Assets | [2] | 0.00% | 10.65%
Total Capital (to Risk Weighted Assets) [Abstract] |  |  |
Total Capital Ratio Required to be Well Capitalized | [2] | 10.00% | 10.00%
Minimum Capital Requirement, Total Capital to Risk Weighted Assets | [2] | 8.00% | 8.00%
Minimum Capital Requirement Including Capital Conservation Buffer, Total Capital to Risk Weighted Assets | [2] | 8.00% | 8.00%
Total Capital | [2] | $ 0 | $ 382,944
Total Capital to Risk Weighted Assets | [2] | 0.00% | 12.83%
Tier 1 Capital (to Average Assets) [Abstract] |  |  |
Leverage Ratio Required to be Well Capitalized | [2] | 5.00% | 5.00%
Minimum Capital Requirement, Tier 1 Capital to Average Assets | [2] | 4.00% | 4.00%
Minimum Capital Requirements Including Capital Conservation Buffer, Tier 1 Capital to Average Assets | [2] | 4.00% | 4.00%
Tier 1 Leverage Capital | [2] | $ 0 | $ 317,944
Tier 1 Capital to Average Assets | [2] | 0.00% | 8.25%
[1] | Capital conservation buffer was effective January 1, 2016 and phased in through 2019. The phased in capital conservation buffer was 2.50% at December 31, 2019 and 1.875% at December 31, 2018. The fully phased in requirement of 2.50% is included in the table above.
[2] | CoBiz Bank was acquired by BOK Financial effective October 1, 2018 and merged into BOKF, NA during the first quarter of 2019.

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- Definition The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826 + Details
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- Definition The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958570-112826 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1H -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=117337116&loc=d3e65071-112826 + Details
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- Definition The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826 + Details
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