XML 48 R53.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans And Allowance For Credit Losses (Summary Of Selected Information On TDRs That Includes Recorded Investment On An Accruing And Nonaccruing Basis By Loan Class And Modification Type) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 9 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Sep. 30, 2012
Sep. 30, 2011
Dec. 31, 2014
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment $ 2,424us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 $ 327us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 $ 74,500us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 $ 142,400us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1  
Recorded investment resulting from the following modification types 309,429us-gaap_FinancingReceivableModificationsRecordedInvestment       343,329us-gaap_FinancingReceivableModificationsRecordedInvestment
1-4 family residential 5,212,963us-gaap_LoansAndLeasesReceivableConsumerMortgage       5,200,882us-gaap_LoansAndLeasesReceivableConsumerMortgage
Construction and other consumer real estate 373,335us-gaap_LoansAndLeasesReceivableConsumerConstruction       370,542us-gaap_LoansAndLeasesReceivableConsumerConstruction
Commercial and industrial 13,264,092us-gaap_LoansReceivableCommercialAndIndustrial       13,162,955us-gaap_LoansReceivableCommercialAndIndustrial
Home equity credit line 2,314,806us-gaap_LoansAndLeasesReceivableConsumerHomeEquity       2,321,150us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
Bankcard and other revolving plans 406,723us-gaap_LoansAndLeasesReceivableConsumerRevolvingCreditCard       401,352us-gaap_LoansAndLeasesReceivableConsumerRevolvingCreditCard
Commercial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 13,264,092us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember		       13,162,955us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialPortfolioSegmentMember
Consumer Portfolio Segment [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 5,212,963us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		       5,200,882us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Construction and other consumer real estate 373,335us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		       370,542us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Home equity credit line 2,314,806us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		       2,321,150us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Bankcard and other revolving plans 406,723us-gaap_LoansAndLeasesReceivableConsumerRevolvingCreditCard
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		       401,352us-gaap_LoansAndLeasesReceivableConsumerRevolvingCreditCard
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 44us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember		      
Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 986us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember		      
Commercial Loan [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 1,030us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember		      
Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 1,284us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember		      
Term [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember		 84us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember		      
Commercial Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 1,284us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember		 84us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember		      
Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 217us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		      
One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 110us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember		      
Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember		 26us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember		      
Consumer Loan [Member]          
Financing Receivable, Modifications [Line Items]          
Financing Receivable, Modifications, Subsequent Default, Recorded Investment 110us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerLoanMember		 243us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerLoanMember		      
Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 28,532us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember		        
Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 51,041us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember		        
Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 14,222us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember		        
Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 44,424us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember		        
Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 13,580us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember		        
Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 45,340us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember		        
Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 1,926us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember		        
Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 36,133us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember		        
Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 17,876us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember		        
Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,027us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember		       1,056us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 21,976us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember		        
Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 15,716us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember		        
Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 1,066us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		        
Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 16,164us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember		        
Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 406us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember		        
Interest Rate Below Market [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 49,456us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		       53,842us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember
Interest Rate Below Market [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 2,509us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 19,744us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 7,238us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 741us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 2,402us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 284us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 322us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 2,328us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types         0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember
Interest Rate Below Market [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 10,901us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 2,780us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 0us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 207us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Interest Rate Below Market [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_InterestRateBelowMarketMember		        
Maturity Or Term Extension [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 9,680us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		       22,115us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember
Maturity Or Term Extension [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 3,462us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,092us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,019us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 84us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 366us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 416us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 515us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,163us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,027us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		       1,056us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 66us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 0us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 227us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Maturity Or Term Extension [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 243us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MaturityOrTeamExtensionMember		        
Principal Forgiveness [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 23,009us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		       21,718us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember
Principal Forgiveness [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 17us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 952us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 176us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 10,968us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 7,073us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 0us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		       0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember
Principal Forgiveness [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 865us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 713us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 2,245us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Principal Forgiveness [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PrincipalForgivenessMember		        
Payment Deferral [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 9,990us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		       10,124us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember
Payment Deferral [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 464us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,241us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 973us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 442us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 3,310us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 833us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		       0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember
Payment Deferral [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 93us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 2,170us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 203us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 185us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Payment Deferral [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 76us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_PaymentDeferralMember		        
Other Recorded Investment Resulting From Following Modification [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 31,666us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]       33,956us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 151us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 10,845us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 510us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 2,289us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 164us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 1,381us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 6,951us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 2,525us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		       0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 3,249us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 0us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 3,601us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Other Recorded Investment Resulting From Following Modification [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 0us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_OtherRecordedInvestmentResultingFromFollowingModificationMember		 [1]        
Multiple Modification Types [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 185,628us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]       201,574us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]
Multiple Modification Types [Member] | Accruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 21,929us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 17,167us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 13,712us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 32,729us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | Home Equity Credit Line [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 1,623us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_HomeEquityCreditLineMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 33,676us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Accruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate 1,226us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_AccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Commercial And Industrial [Member]          
Financing Receivable, Modifications [Line Items]          
Commercial and industrial 25,035us-gaap_LoansReceivableCommercialAndIndustrial
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Owner Occupied [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 11,027us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Municipal [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		       0us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_MunicipalMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember
Multiple Modification Types [Member] | Nonaccruing [Member] | Commercial Real Estate Construction Financing Receivable [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 7,667us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateConstructionFinancingReceivableMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Term [Member]          
Financing Receivable, Modifications [Line Items]          
Recorded investment resulting from the following modification types 9,901us-gaap_FinancingReceivableModificationsRecordedInvestment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_TermMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Home Equity Line of Credit [Member]          
Financing Receivable, Modifications [Line Items]          
Home equity credit line 150us-gaap_LoansAndLeasesReceivableConsumerHomeEquity
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | One Through Four Family Residential [Member]          
Financing Receivable, Modifications [Line Items]          
1-4 family residential 9,699us-gaap_LoansAndLeasesReceivableConsumerMortgage
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_OneThroughFourFamilyResidentialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
Multiple Modification Types [Member] | Nonaccruing [Member] | Construction And Other Consumer Real Estate [Member]          
Financing Receivable, Modifications [Line Items]          
Construction and other consumer real estate $ 87us-gaap_LoansAndLeasesReceivableConsumerConstruction
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= zion_NonaccruingMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= zion_ConstructionAndOtherConsumerRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= zion_MultipleModificationTypesMember		 [2]        
[1] Includes TDRs that resulted from other modification types including, but not limited to, a legal judgment awarded on different terms, a bankruptcy plan confirmed on different terms, a settlement that includes the delivery of collateral in exchange for debt reduction, etc.
[2] Includes TDRs that resulted from a combination of any of the previous modification types.