Loans, Leases, and Allowance for Credit Losses (Summary of Financial Impact of Loan Modifications) (Details)	3 Months Ended
Mar. 31, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	4.00%
Weighted-average term extension (in months)	10 months
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	4.40%
Weighted-average term extension (in months)	9 months
Commercial \| Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	0.00%
Weighted-average term extension (in months)	10 months
Commercial \| Owner-occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	4.40%
Weighted-average term extension (in months)	5 months
Commercial \| Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	0.00%
Weighted-average term extension (in months)	6 months
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	0.00%
Weighted-average term extension (in months)	9 months
Commercial real estate \| Term
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	0.00%
Weighted-average term extension (in months)	9 months
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	1.30%
Weighted-average term extension (in months)	84 months
Consumer \| 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	1.30%
Weighted-average term extension (in months)	110 months
Consumer \| Bankcard and other revolving plans
Financing Receivable, Allowance for Credit Losses [Line Items]
Weighted-average interest rate reduction (in percentage points)	0.00%
Weighted-average term extension (in months)	65 months

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph c
-Publisher SEC

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageInterestRateDecreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModifiedWeightedAverageTermIncreaseFromModification
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_OwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_ConstructionAndLandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_TermMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_OneThroughFourFamilyResidentialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=zions_BankcardAndOtherRevolvingPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: