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v3.25.3

BASIS OF PRESENTATION (Details) | 9 Months Ended
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Sep. 30, 2025 segment state
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Number of states in which entity operates | state | 11
Number of bank operating segments | segment | 7

X
- Definition The number of states the entity operates in as of the balance sheet date. + References No definition available. + Details
Name: | us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

X
- Definition Number Of Bank Operating Segments + References No definition available. + Details
Name: | zions_NumberOfBankOperatingSegments
Namespace Prefix: | zions_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration