OPERATING SEGMENT INFORMATION - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 branch segment	Sep. 23, 2024 USD ($) branch
Segment Reporting Information [Line Items]
Number of bank operating segments | segment	7
Number of branches	409
CB&T
Segment Reporting Information [Line Items]
Number Of Branches To Be Acquired		4
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Deposits | $		$ 700
Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Financing Receivables | $		$ 400
Utah | Zions Bank
Segment Reporting Information [Line Items]
Number of branches	95
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	75
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	34
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