Basis of Presentaion Organization and Presentation (Policies)	6 Months Ended
Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	BASIS OF PRESENTATION The accompanying unaudited consolidated financial statements of Zions Bancorporation (“the Parent”) and its majority-owned subsidiaries (collectively “the Company,” “Zions,” “we,” “our,” “us”) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. References to GAAP, including standards promulgated by the Financial Accounting Standards Board (“FASB”), are made according to sections of the Accounting Standards Codification (“ASC”). Changes to the ASC are made with Accounting Standards Updates (“ASU”) that include consensus issues of the Emerging Issues Task Force (“EITF”). In certain cases, ASUs are issued jointly with International Financial Reporting Standards (“IFRS”). Operating results for the six months ended June 30, 2017 and 2016 are not necessarily indicative of the results that may be expected in future periods. In preparing the consolidated financial statements, we are required to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. The consolidated balance sheet at December 31, 2016 is from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in the Company’s 2016 Annual Report on Form 10-K. Certain prior period amounts have been reclassified to conform with the current period presentation. These reclassifications did not affect net income or shareholders’ equity. Zions Bancorporation (“the Parent”) is a financial holding company headquartered in Salt Lake City, Utah, which owns and operates a commercial bank. The Parent and its subsidiaries (collectively “the Company”) provide a full range of banking and related services in 11 Western and Southwestern states through seven separately managed and branded units as follows: Zions Bank, in Utah, Idaho and Wyoming; California Bank & Trust (“CB&T”); Amegy Bank (“Amegy”), in Texas; National Bank of Arizona (“NBAZ”); Nevada State Bank (“NSB”); Vectra Bank Colorado (“Vectra”), in Colorado and New Mexico; and The Commerce Bank of Washington (“TCBW”) which operates under that name in Washington and under the name The Commerce Bank of Oregon (“TCBO”) in Oregon. The Parent also owns and operates certain nonbank subsidiaries that engage in financial services.

BASIS OF PRESENTATION

The accompanying unaudited consolidated financial statements of Zions Bancorporation (“the Parent”) and its majority-owned subsidiaries (collectively “the Company,” “Zions,” “we,” “our,” “us”) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. References to GAAP, including standards promulgated by the Financial Accounting Standards Board (“FASB”), are made according to sections of the Accounting Standards Codification (“ASC”). Changes to the ASC are made with Accounting Standards Updates (“ASU”) that include consensus issues of the Emerging Issues Task Force (“EITF”). In certain cases, ASUs are issued jointly with International Financial Reporting Standards (“IFRS”).

Operating results for the six months ended June 30, 2017 and 2016 are not necessarily indicative of the results that may be expected in future periods. In preparing the consolidated financial statements, we are required to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. The consolidated balance sheet at December 31, 2016 is from the audited financial statements at that date, but does not include all of the information and footnotes required by GAAP for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in the Company’s 2016 Annual Report on Form 10-K. Certain prior period amounts have been reclassified to conform with the current period presentation. These reclassifications did not affect net income or shareholders’ equity.

Zions Bancorporation (“the Parent”) is a financial holding company headquartered in Salt Lake City, Utah, which owns and operates a commercial bank. The Parent and its subsidiaries (collectively “the Company”) provide a full range of banking and related services in 11 Western and Southwestern states through seven separately managed and branded units as follows: Zions Bank, in Utah, Idaho and Wyoming; California Bank & Trust (“CB&T”); Amegy Bank (“Amegy”), in Texas; National Bank of Arizona (“NBAZ”); Nevada State Bank (“NSB”); Vectra Bank Colorado (“Vectra”), in Colorado and New Mexico; and The Commerce Bank of Washington (“TCBW”) which operates under that name in Washington and under the name The Commerce Bank of Oregon (“TCBO”) in Oregon. The Parent also owns and operates certain nonbank subsidiaries that engage in financial services.