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BASIS OF PRESENTATION (Details)	9 Months Ended
	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