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OPERATING SEGMENT INFORMATION (Narrative) (Details)	9 Months Ended
	Sep. 30, 2025 branch segment
Segment Reporting Information [Line Items]
Number of bank operating segments | segment	7
Number of branches	408
Utah | Zions Bank
Segment Reporting Information [Line Items]
Number of branches	93
Idaho | Zions Bank
Segment Reporting Information [Line Items]
Number of branches	25
Wyoming | Zions Bank
Segment Reporting Information [Line Items]
Number of branches	1
California | CB&T
Segment Reporting Information [Line Items]
Number of branches	77
California | CB&T | FirstBank Coachella Valley Branches
Segment Reporting Information [Line Items]
Number of branches	4
Texas | Amegy
Segment Reporting Information [Line Items]
Number of branches	76
Arizona | NBAZ
Segment Reporting Information [Line Items]
Number of branches	56
Nevada | NSB
Segment Reporting Information [Line Items]
Number of branches	43
Colorado | Vectra
Segment Reporting Information [Line Items]
Number of branches	33
New Mexico | Vectra
Segment Reporting Information [Line Items]
Number of branches	1
Washington | TCBW
Segment Reporting Information [Line Items]
Number of branches	2
Oregon | TCBW
Segment Reporting Information [Line Items]
Number of branches	1

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- Definition

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- Definition

Number Of Bank Operating Segments

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- Definition

Number of Branches

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- Details

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