Name:	srt_RegulatoryCapitalRequirementsAbstract
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Capital conservation buffer percentage calculated as Common Equity Tier 1 risk-based capital ratio after deduction of minimum Common Equity Tier 1 risk-based capital ratio as defined by regulatory framework.

Name:	us-gaap_BankingRegulationCapitalConservationBufferCommonEquityTierOneRiskBasedCapitalActual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Capital conservation buffer percentage calculated as Tier 1 risk-based capital ratio after deduction of minimum Tier 1 risk-based capital ratio as defined by regulatory framework.

Name:	us-gaap_BankingRegulationCapitalConservationBufferTierOneRiskBasedCapitalActual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Capital conservation buffer percentage calculated as total risk-based capital ratio after deduction of minimum total risk-based capital ratio as defined by regulatory framework.

Name:	us-gaap_BankingRegulationCapitalConservationBufferTotalRiskBasedCapitalActual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of minimum Common Equity Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477270/942-505-50-1B

Name:	us-gaap_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioCapitalAdequacyMinimum
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

Name:	us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of total risk-based capital to risk-weighted assets as defined by regulatory framework.

Name:	us-gaap_CapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of Common Equity Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework.

Name:	us-gaap_CommonEquityTierOneCapitalRatio
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of total risk-based capital to risk-weighted assets exceeding minimum required for capital adequacy as defined by regulatory framework.

Name:	us-gaap_ExcessCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of Tier 1 risk-based capital to risk-weighted assets exceeding minimum required for capital adequacy as defined by regulatory framework.

Name:	us-gaap_ExcessTierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of minimum Tier 1 leverage capital to average assets required for capital adequacy as defined by regulatory framework.

Name:	us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of Tier 1 capital to average assets as defined by regulatory framework.

Name:	us-gaap_TierOneLeverageCapitalToAverageAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of minimum Tier 1 risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

Name:	us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Ratio of Tier 1 risk-based capital to risk-weighted assets as defined by regulatory framework.

Name:	us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Banking Regulation, Common Equity Tier One Risk-Based Capital Ratio, Excess, Actual

No definition available.

Name:	zions_BankingRegulationCommonEquityTierOneRiskBasedCapitalRatioExcessActual
Namespace Prefix:	zions_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Banking Regulation, Tier 1 Leverage Capital Ratio, Excess Actual

No definition available.

ZIONS BANCORPORATION, NATIONAL ASSOCIATION /UT/ 10-K