XML 82 R60.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans, Leases and Allowance for Credit Losses - Troubled Debt Restructured Loans by Class for Which There was Payment Default (Detail) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
SecurityLoan
Mar. 31, 2014
SecurityLoan
Financing Receivable, Modifications [Line Items]    
Number of Loans 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 3us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Recorded Investment $ 137us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 $ 568us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Residential real estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ResidentialRealEstateMember		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ResidentialRealEstateMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ResidentialRealEstateMember		 202us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ResidentialRealEstateMember
Consumer [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ConsumerLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ConsumerLoanMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ConsumerLoanMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_ConsumerLoanMember
Owner occupied [Member] | Commercial real estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 303us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Non-owner occupied [Member] | Commercial real estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Multi-family [Member] | Commercial real estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateMultiFamilyMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateMultiFamilyMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateMultiFamilyMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialRealEstateMultiFamilyMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_CommercialRealEstateMember
Commercial [Member] | Commercial and industrial [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialCommercialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember		 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialCommercialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialCommercialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember		 63us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialCommercialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember
Leases [Member] | Commercial and industrial [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialLeasesMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialLeasesMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember
Recorded Investment 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialLeasesMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_CommercialAndIndustrialLeasesMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_CommercialAndIndustrialMember
Construction [Member] | Construction and land development [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 1us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_ConstructionAndLandDevelopmentConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_ConstructionAndLandDevelopmentConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember
Recorded Investment 137us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_ConstructionAndLandDevelopmentConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= wal_ConstructionAndLandDevelopmentConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember
Land [Member] | Construction and land development [Member]    
Financing Receivable, Modifications [Line Items]    
Number of Loans 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_LandMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember		 0us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_LandMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember
Recorded Investment $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_LandMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember		 $ 0us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_LandMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= wal_ConstructionAndLandDevelopmentLandMember