$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

$wal Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-Q Financial Statement

#000121254519000115 Filed on October 31, 2019

Income Statement

Concept	2019 Q4	2019 Q3	2018 Q3
Revenue	$315.4M	$315.6M	$265.2M
YoY Change	11.86%	19.0%	21.75%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$5.000M	$4.700M	$3.700M
YoY Change	31.58%	27.03%	2.78%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$43.40M	$49.20M	$31.18M
YoY Change	12.86%	57.8%	91.83%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$154.3M	$155.8M	$118.6M
YoY Change	10.22%	31.35%	0.74%
Income Tax	$26.20M	$28.50M	$7.492M
% Of Pretax Income	16.98%	18.29%	6.32%
Net Earnings	$128.1M	$127.3M	$111.1M
YoY Change	7.57%	14.56%	34.14%
Net Earnings / Revenue	40.62%	40.34%	41.9%
Basic Earnings Per Share	$1.26	$1.25	$1.06
Diluted Earnings Per Share	$1.25	$1.24	$1.05
COMMON SHARES
Basic Shares Outstanding	102.6M shares	102.0M shares	104.8M shares
Diluted Shares Outstanding		102.5M shares	105.4M shares

Balance Sheet

Concept	2019 Q4	2019 Q3	2018 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$434.6M	$872.1M	$700.6M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$125.8M	$125.1M	$119.2M
YoY Change	5.29%	4.91%	-0.71%
Goodwill	$289.9M	$289.9M	$289.9M
YoY Change	0.0%	0.0%	0.0%
Intangibles	$7.713M	$8.099M	$9.658M
YoY Change	-16.71%	-16.14%	-14.24%
Long-Term Investments	$139.0M	$127.0M	$172.0M
YoY Change	20.87%	-26.16%
Other Assets	$18.00M	$4.000M	$43.00M
YoY Change	-43.75%	-90.7%	-48.81%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$26.82B	$26.32B	$22.18B
YoY Change	16.06%	18.71%	11.31%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$78.00M	$80.00M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change	-100.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$78.00M	$80.00M	$21.00M
YoY Change	254.55%	280.95%	-19.23%
LONG-TERM LIABILITIES
Long-Term Debt	$394.0M	$389.0M	$359.0M
YoY Change	9.44%	8.36%	-3.75%
Other Long-Term Liabilities	$520.0M	$477.0M	$399.0M
YoY Change	17.12%	19.55%	-15.64%
Total Long-Term Liabilities	$914.0M	$866.0M	$758.0M
YoY Change	13.68%	14.25%	-10.4%
TOTAL LIABILITIES
Total Short-Term Liabilities	$78.00M	$80.00M	$21.00M
Total Long-Term Liabilities	$914.0M	$866.0M	$758.0M
Total Liabilities	$23.81B	$23.40B	$19.69B
YoY Change	16.15%	18.86%	10.75%
SHAREHOLDERS EQUITY
Retained Earnings	$1.680B	$1.582B	$1.166B
YoY Change	31.0%	35.65%	53.73%
Common Stock	$10.00K	$10.00K	$10.00K
YoY Change	0.0%	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$62.70M	$62.67M	$52.04M
YoY Change	18.12%	20.43%	30.07%
Treasury Stock Shares	2.004M shares
Shareholders Equity	$3.017B	$2.923B	$2.488B
YoY Change
Total Liabilities & Shareholders Equity	$26.82B	$26.32B	$22.18B
YoY Change	16.06%	18.71%	11.31%

Cashflow Statement

Concept	2019 Q4	2019 Q3	2018 Q3
OPERATING ACTIVITIES
Net Income	$128.1M	$127.3M	$111.1M
YoY Change	7.57%	14.56%	34.14%
Depreciation, Depletion And Amortization	$5.000M	$4.700M	$3.700M
YoY Change	31.58%	27.03%	2.78%
Cash From Operating Activities	$183.3M	$204.2M	$148.9M
YoY Change	26.68%	37.14%	55.59%
INVESTING ACTIVITIES
Capital Expenditures	-$19.80M	-$6.100M	-$6.500M
YoY Change	560.0%	-6.15%	160.0%
Acquisitions
YoY Change
Other Investing Activities	-$928.0M	-$1.325B	-$696.6M
YoY Change	-13.13%	90.2%	-23.74%
Cash From Investing Activities	-$947.8M	-$1.331B	-$703.2M
YoY Change	-11.52%	89.28%	-23.22%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	327.1M	931.2M	748.0M
YoY Change	-54.86%	24.49%	-13.43%
NET CHANGE
Cash From Operating Activities	183.3M	204.2M	148.9M
Cash From Investing Activities	-947.8M	-1.331B	-703.2M
Cash From Financing Activities	327.1M	931.2M	748.0M
Net Change In Cash	-437.4M	-195.6M	193.7M
YoY Change	116.64%	-200.98%	342.24%
FREE CASH FLOW
Cash From Operating Activities	$183.3M	$204.2M	$148.9M
Capital Expenditures	-$19.80M	-$6.100M	-$6.500M
Free Cash Flow	$203.1M	$210.3M	$155.4M
YoY Change	37.51%	35.33%	58.25%

Facts In Submission

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	dei	Entity Registrant Name EntityRegistrantName	WESTERN ALLIANCE BANCORPORATION
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	dei	Entity Address City Or Town EntityAddressCityOrTown	Phoenix
	dei	Entity Address State Or Province EntityAddressStateOrProvince	AZ
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	dei	City Area Code CityAreaCode	602
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CY2018Q3	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5267000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	17121000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	16684000	USD
CY2019Q3	wal	Incomefrom Equity Investments IncomefromEquityInvestments	3742000	USD
CY2018Q3	wal	Incomefrom Equity Investments IncomefromEquityInvestments	1440000	USD
	wal	Incomefrom Equity Investments IncomefromEquityInvestments	6619000	USD
	wal	Incomefrom Equity Investments IncomefromEquityInvestments	5417000	USD
CY2018Q3	wal	Card Income CardIncome	2138000	USD
	wal	Card Income CardIncome	5195000	USD
	wal	Card Income CardIncome	6143000	USD
CY2019Q3	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	1321000	USD
CY2018Q3	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	1092000	USD
	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	3564000	USD
	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	3475000	USD
CY2019Q3	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	979000	USD
CY2018Q3	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	868000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2938000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2963000	USD
CY2019Q3	wal	Lendingrelatedfees Lendingrelatedfees	539000	USD
CY2018Q3	wal	Lendingrelatedfees Lendingrelatedfees	1422000	USD
	wal	Lendingrelatedfees Lendingrelatedfees	1343000	USD
	wal	Lendingrelatedfees Lendingrelatedfees	3447000	USD
CY2019Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
CY2018Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	-7232000	USD
	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	-7232000	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	222000	USD
CY2018Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-1212000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4628000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-2971000	USD
CY2019Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1869000	USD
CY2018Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	635000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4509000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1579000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	4418000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
	us-gaap	Noninterest Income NoninterestIncome	29505000	USD
CY2019Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	70978000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	188680000	USD
CY2019Q3	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	11537000	USD
CY2018Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	64762000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	205328000	USD
CY2018Q3	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	4848000	USD
	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	24930000	USD
CY2018Q3	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	7907000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	26885000	USD
CY2018Q3	us-gaap	Business Development BusinessDevelopment	1381000	USD
	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	11888000	USD
CY2019Q3	us-gaap	Occupancy Net OccupancyNet	8263000	USD
CY2018Q3	us-gaap	Occupancy Net OccupancyNet	7406000	USD
	us-gaap	Occupancy Net OccupancyNet	24251000	USD
	us-gaap	Occupancy Net OccupancyNet	21671000	USD
CY2019Q3	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	8248000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	21856000	USD
CY2019Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	7095000	USD
CY2018Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	5895000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	20563000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	16688000	USD
CY2019Q3	us-gaap	General Insurance Expense GeneralInsuranceExpense	3071000	USD
CY2018Q3	us-gaap	General Insurance Expense GeneralInsuranceExpense	3712000	USD
	us-gaap	General Insurance Expense GeneralInsuranceExpense	8691000	USD
	us-gaap	General Insurance Expense GeneralInsuranceExpense	11466000	USD
CY2019Q3	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	1953000	USD
CY2018Q3	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	1230000	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	5419000	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	2830000	USD
CY2019Q3	us-gaap	Business Development BusinessDevelopment	1443000	USD
	us-gaap	Business Development BusinessDevelopment	4972000	USD
	us-gaap	Business Development BusinessDevelopment	4523000	USD
CY2019Q3	us-gaap	Marketing Expense MarketingExpense	842000	USD
CY2018Q3	us-gaap	Marketing Expense MarketingExpense	687000	USD
	us-gaap	Marketing Expense MarketingExpense	2640000	USD
	us-gaap	Marketing Expense MarketingExpense	2429000	USD
CY2019Q3	wal	Cardexpense Cardexpense	548000	USD
CY2018Q3	wal	Cardexpense Cardexpense	1282000	USD
	wal	Cardexpense Cardexpense	1892000	USD
	wal	Cardexpense Cardexpense	3305000	USD
CY2019Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	387000	USD
CY2018Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	398000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1161000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1195000	USD
CY2019Q3	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	3379000	USD
CY2018Q3	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-67000	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	2856000	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-1474000	USD
CY2019Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8211000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	125955000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	29481000	USD
	us-gaap	Noninterest Expense NoninterestExpense	353082000	USD
	us-gaap	Noninterest Expense NoninterestExpense	314538000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	155908000	USD
CY2018Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	14400000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	23494000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	118615000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	449926000	USD
CY2018Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105448000	shares
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	370333000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28533000	USD
CY2018Q3	us-gaap	Noninterest Expense NoninterestExpense	113841000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7492000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	78819000	USD
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103468000	shares
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	53631000	USD
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105398000	shares
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	111123000	USD
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102041000	shares
CY2018Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104768000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	103024000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104664000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	102451000	shares
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Net Income Loss NetIncomeLoss	316702000	USD
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.03
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.05
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.59
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.00
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	111123000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Net Income Loss NetIncomeLoss	316702000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	11014000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-22462000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	78314000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-71765000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	18000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	12000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	53000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	35000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	598000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	6060000	USD
CY2019Q3	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	1531000	USD
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	-43658000	USD
CY2019Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	-25684000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-2028000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-6664000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	186000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5454000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5454000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-19048000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-66160000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	136593000	USD
CY2018Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	92075000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	440328000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	250542000	USD
CY2018Q2	us-gaap	Stockholders Equity StockholdersEquity	2391684000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	111123000	USD
CY2018Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	5698000	USD
CY2018Q3	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	1064000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-19048000	USD
CY2018Q3	us-gaap	Stockholders Equity StockholdersEquity	2488393000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	2851264000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	19000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2923063000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	2229698000	USD
CY2018Q1	us-gaap	Stockholders Equity StockholdersEquity	2229698000	USD
	us-gaap	Net Income Loss NetIncomeLoss	316702000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	534000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	19481000	USD
	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	11862000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-66160000	USD
CY2018Q3	us-gaap	Stockholders Equity StockholdersEquity	2488393000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2613734000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	55000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	19783000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	5757000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2963000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	3152000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	-7232000	USD
	us-gaap	Restricted Stock Award Forfeitures RestrictedStockAwardForfeitures	9582000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	-115571000	USD
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	-25684000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2923063000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Net Income Loss NetIncomeLoss	316702000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	14500000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17000000	USD
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	13512000	USD
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	10460000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	19783000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	19481000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-16107000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-11031000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-10795000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	33551000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	26546000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	7704000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	0	USD
	wal	Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitionsof Loans AccretionAndAmortizationFairMarketValueAdjustmentsRelatingToAcquisitionsofLoans	10141000	USD
	wal	Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitionsof Loans AccretionAndAmortizationFairMarketValueAdjustmentsRelatingToAcquisitionsofLoans	14099000	USD
	wal	Accretionand Amortization Fair Market Value Adjustments Relatingto Acquisitionsof Other Assetsand Liabilities AccretionandAmortizationFairMarketValueAdjustmentsRelatingtoAcquisitionsofOtherAssetsandLiabilities	-1392000	USD
	wal	Accretionand Amortization Fair Market Value Adjustments Relatingto Acquisitionsof Other Assetsand Liabilities AccretionandAmortizationFairMarketValueAdjustmentsRelatingtoAcquisitionsofOtherAssetsandLiabilities	-1427000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2938000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4628000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-2971000	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	-530000	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2434000	USD
	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	628000	USD
	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	1464000	USD
	wal	Valuation Adjustments Of Other Repossessed Assets Net ValuationAdjustmentsOfOtherRepossessedAssetsNet	-3221000	USD
	wal	Valuation Adjustments Of Other Repossessed Assets Net ValuationAdjustmentsOfOtherRepossessedAssetsNet	-32000	USD
	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-263000	USD
	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	42000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-73641000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-20743000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	534505000	USD
	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	-5000	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1655000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	396280000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	746445000	USD
	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	244000	USD
	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	208000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	2445769000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	1591733000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	15282000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	8319000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	251413000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	55000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	534000	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	66456000	USD
	wal	Restrictedstocksurrendered Restrictedstocksurrendered	9582000	USD
	wal	Restrictedstocksurrendered Restrictedstocksurrendered	11862000	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	5298000	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	3063000	USD
	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	7000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	115571000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	453307000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	329958000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	150377000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	44308000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	100460000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	34275000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	18206000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	754000	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	10000000	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	10662000	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	71727000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	4535000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	-426000	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	88074000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	628000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	8793000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-2775174000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1642157000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	3263367000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	1936048000	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-498429000	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-395047000	USD
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	25684000	USD
	us-gaap	Payments Of Dividends Preferred Stock And Preference Stock PaymentsOfDividendsPreferredStockAndPreferenceStock	0	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2614156000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	1529673000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	373487000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	283796000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	498572000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	416768000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	872059000	USD
CY2018Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	700564000	USD
	us-gaap	Interest Paid InterestPaid	144680000	USD
	us-gaap	Interest Paid InterestPaid	81247000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-26228000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	14658000	USD
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	898000	USD
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	5744000	USD
	wal	Unfunded Commitments To Purchase Investment Tax Credits UnfundedCommitmentsToPurchaseInvestmentTaxCredits	148110000	USD
	wal	Unfunded Commitments To Purchase Investment Tax Credits UnfundedCommitmentsToPurchaseInvestmentTaxCredits	65639000	USD
	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	75938000	USD
	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	-66311000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-6664000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	186000	USD
	wal	Changein Unfunded Obligations Non Cash ChangeinUnfundedObligationsNonCash	-33312000	USD
	wal	Changein Unfunded Obligations Non Cash ChangeinUnfundedObligationsNonCash	82270000	USD
	us-gaap	Noncash Contribution Expense NoncashContributionExpense	0	USD
	us-gaap	Noncash Contribution Expense NoncashContributionExpense	6895000	USD
	wal	Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries NumberOfWhollyOwnedSubsidiariesNonBankSubsidiaries	2	Subsidiary
CY2018Q4	wal	Number Of Securities In Unrealized Position NumberOfSecuritiesInUnrealizedPosition	373	positions
	us-gaap	Use Of Estimates UseOfEstimates	<div style="line-height:120%;padding-top:12px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Use of estimates</span></div><div style="line-height:120%;padding-top:12px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management's estimates and judgments are ongoing and are based on experience, current and expected future conditions, third-party evaluations and various other assumptions that management believes are reasonable under the circumstances. The results of these estimates form the basis for making judgments about the carrying values of assets and liabilities, as well as identifying and assessing the accounting treatment with respect to commitments and contingencies. Actual results may differ from those estimates and assumptions used in the Consolidated Financial Statements and related notes. Material estimates that are particularly susceptible to significant changes in the near term relate to: the determination of the allowance for credit losses; certain assets and liabilities carried at fair value; and accounting for income taxes. </span></div>
	wal	Number Of Unconsolidated Subsidiaries NumberOfUnconsolidatedSubsidiaries	8	Subsidiary
	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="line-height:120%;padding-top:12px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;font-weight:bold;">Reclassifications</span></div><div style="line-height:120%;padding-top:12px;text-align:justify;font-size:10pt;"><span style="font-family:inherit;font-size:10pt;">Certain amounts reported in prior periods may have been reclassified in the Consolidated Financial Statements to conform to the current presentation. The reclassifications have no effect on net income or stockholders’ equity as previously reported.</span></div>
CY2019Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2019Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	482069000	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	126502000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	302905000	USD
CY2018Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	3251000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	3163000	USD
CY2019Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	442396000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	39673000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3475037000	USD
CY2019Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	60426000	USD
CY2019Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	22635000	USD
CY2019Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3512828000	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	123611000	USD
CY2019Q3	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	3233000	USD
CY2019Q3	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	342000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	7420000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	298648000	USD
CY2018Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3339888000	USD
CY2018Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	22054000	USD
CY2018Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	84954000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	115061000	USD
CY2019Q3	wal	Number Of Securities In Unrealized Position NumberOfSecuritiesInUnrealizedPosition	146	positions
	us-gaap	Other Than Temporary Impairment Losses Investments Portion In Other Comprehensive Income Loss Before Tax Including Portion Attributable To Noncontrolling Interest OtherThanTemporaryImpairmentLossesInvestmentsPortionInOtherComprehensiveIncomeLossBeforeTaxIncludingPortionAttributableToNoncontrollingInterest	0	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	2322000	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	565726000	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	20313000	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	690997000	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	22635000	USD
CY2019Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	1256723000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	10114000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	574255000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	74840000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	2086619000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	84954000	USD
CY2018Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	2660874000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	24841000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	25515000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	417555000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	456554000	USD
CY2019Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	442396000	USD
CY2019Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	482069000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	3273000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	3272000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	23323000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	23580000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	191209000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	184775000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	467042000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	499353000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost	2790190000	USD
CY2019Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	2801848000	USD
CY2019Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3475037000	USD
CY2018Q3	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	0	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3152000	USD
CY2019Q3	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3152000	USD
CY2019Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3512828000	USD
CY2019Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3512828000	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	126502000	USD
CY2018Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3276988000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	115061000	USD
CY2019Q3	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	967400000	USD
CY2018Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	788400000	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	0	USD
CY2019Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
CY2018Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	-7232000	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	-7232000	USD
CY2019Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
CY2018Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	-7232000	USD
	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	-7232000	USD
	us-gaap	Debt Securities Held To Maturity Sold Amount DebtSecuritiesHeldToMaturitySoldAmount	10000000.0	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	20131058000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	165021000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	152717000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	19966037000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	17557912000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	44300000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	36300000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2019Q3	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	20900000	USD
CY2018Q4	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	2000000.0	USD
CY2019Q3	wal	Interest Rate Markson Acquired Loans InterestRateMarksonAcquiredLoans	4300000	USD
CY2018Q4	wal	Interest Rate Markson Acquired Loans InterestRateMarksonAcquiredLoans	7100000	USD
CY2019Q3	wal	Credit Markon Acquired Loans CreditMarkonAcquiredLoans	7500000	USD
CY2018Q4	wal	Credit Markon Acquired Loans CreditMarkonAcquiredLoans	14600000	USD
CY2019Q3	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	21800000	USD
CY2018Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	0	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	20085337000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	45721000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	20131058000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	17673900000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	36729000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	594000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	700000	USD
CY2018Q3	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	600000	USD
	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	1500000	USD
	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	1800000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	20131058000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	20085337000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	20131058000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	17673900000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20813000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	986000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	116978000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	681000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	111266000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	112252000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	137791000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	4314000	USD
	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	4028000	USD
	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	3109000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	594000	USD
CY2019Q3	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	137791000	USD
CY2018Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	112252000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	134102000	USD
CY2018Q3	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	104652000	USD
	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	124688000	USD
	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	100712000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	1334000	USD
CY2018Q3	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	1114000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	50338000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	27746000	USD
CY2019Q3	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2018Q4	wal	Non Performing Loans NonPerformingLoans	64798000	USD
CY2019Q3	us-gaap	Foreclosed Assets ForeclosedAssets	15483000	USD
CY2018Q4	us-gaap	Foreclosed Assets ForeclosedAssets	17924000	USD
CY2019Q3	wal	Non Performing Assets NonPerformingAssets	110811000	USD
CY2018Q4	wal	Non Performing Assets NonPerformingAssets	82722000	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsFromNonaccretableDifference	0	USD
CY2019Q3	wal	Troubled Debt Restructured Loans TroubledDebtRestructuredLoans	44990000	USD
CY2018Q4	wal	Troubled Debt Restructured Loans TroubledDebtRestructuredLoans	36458000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsFromNonaccretableDifference	0	USD
CY2019Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	140000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	443000	USD
	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	801000	USD
CY2019Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	160409000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	2099000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	2711000	USD
CY2019Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	4000000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	165021000	USD
CY2019Q3	wal	Impaired Financing Receivable With No Related Allowance ImpairedFinancingReceivableWithNoRelatedAllowance	0	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	4314000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	160606000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	165021000	USD
CY2018Q3	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	224000	USD
CY2018Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	147083000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	4765000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	1693000	USD
CY2018Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6000000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	150011000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	152717000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	6968000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	4772000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	14500000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	165021000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	140050000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	12290000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	5251000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17000000	USD
CY2018Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	150011000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20813000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	116978000	USD
CY2019Q3	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	137791000	USD
CY2019Q3	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	19935539000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	20131058000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	24310000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	123117000	USD
CY2019Q3	wal	Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment ImpairedFinancingReceivableUnpaidPrincipalBalanceIndividuallyEvaluatedForImpairment	147427000	USD
CY2019Q3	wal	Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment FinancingReceivableUnpaidPrincipalBalanceCollectivelyEvaluatedForImpairment	19924903000	USD
CY2019Q3	wal	Financing Receivable Unpaid Principal Balance FinancingReceivableUnpaidPrincipalBalance	20142465000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	4314000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	986000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	111266000	USD
CY2018Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	112252000	USD
CY2018Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	17514822000	USD
	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	400000	USD
	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2019Q3	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	709071000	USD
CY2018Q3	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	482803000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	3
CY2019Q3	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	11800000	USD
CY2018Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	4
CY2018Q3	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	2800000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	7
	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	40700000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	11
	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	34400000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Gross Carrying Amount LoansAndLeasesReceivableGrossCarryingAmount	17710629000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	1845000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	198234000	USD
CY2018Q4	wal	Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment ImpairedFinancingReceivableUnpaidPrincipalBalanceIndividuallyEvaluatedForImpairment	200079000	USD
CY2018Q4	wal	Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment FinancingReceivableUnpaidPrincipalBalanceCollectivelyEvaluatedForImpairment	17514822000	USD
CY2018Q4	wal	Financing Receivable Unpaid Principal Balance FinancingReceivableUnpaidPrincipalBalance	17820320000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	681000	USD
CY2018Q4	wal	Impaired Financing Receivable With No Related Allowance ImpairedFinancingReceivableWithNoRelatedAllowance	0	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	681000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	151940000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	152717000	USD
	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	1830177000	USD
	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	1010272000	USD
CY2019Q3	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	14238000	USD
CY2018Q3	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	12360000	USD
	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	49068000	USD
	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	46488000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	-17000	USD
CY2018Q3	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	991000	USD
	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	-530000	USD
	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	2434000	USD
CY2019Q3	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	74500000	USD
CY2019Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	79800000	USD
CY2019Q3	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0308
CY2019Q3	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P8Y7M6D
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	3019000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	12117000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	10150000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	8998000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	9060000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	49078000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	92422000	USD
CY2019Q3	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	12619000	USD
CY2019Q3	us-gaap	Operating Lease Liability OperatingLeaseLiability	79803000	USD
CY2019Q3	wal	Lesseeoperatingleaseleasesnotyetcommencedaggregatedcommitment Lesseeoperatingleaseleasesnotyetcommencedaggregatedcommitment	2600000	USD
CY2019Q3	us-gaap	Lease Cost LeaseCost	3200000	USD
	us-gaap	Lease Cost LeaseCost	9500000	USD
CY2019Q3	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	1000000.0	USD
	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	3000000.0	USD
	us-gaap	Operating Lease Payments OperatingLeasePayments	9374000	USD
	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	42917000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Current OperatingLeasesFutureMinimumPaymentsDueCurrent	11370000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Two Years OperatingLeasesFutureMinimumPaymentsDueInTwoYears	10322000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Three Years OperatingLeasesFutureMinimumPaymentsDueInThreeYears	7418000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Four Years OperatingLeasesFutureMinimumPaymentsDueInFourYears	6294000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due In Five Years OperatingLeasesFutureMinimumPaymentsDueInFiveYears	6070000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due Thereafter OperatingLeasesFutureMinimumPaymentsDueThereafter	15417000	USD
CY2018Q4	us-gaap	Operating Leases Future Minimum Payments Due OperatingLeasesFutureMinimumPaymentsDue	56891000	USD
CY2018Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	235000000	USD
CY2019Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	0	USD
CY2019Q3	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	256000000	USD
CY2019Q3	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	0	USD
CY2018Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	491000000	USD
CY2019Q3	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	256000000.0	USD
CY2019Q3	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	0	USD
CY2018Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	235000000.0	USD
CY2018	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Interest Rate For Year FederalHomeLoanBankAdvancesActivityForYearAverageInterestRateForYear	0.0256
CY2019Q3	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	15000000.0	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	22400000	USD
CY2019Q3	us-gaap	Subordinated Debt SubordinatedDebt	318700000	USD
CY2018Q4	us-gaap	Subordinated Debt SubordinatedDebt	299400000	USD
	wal	Numberof Statutory Business Trusts Formedor Acquired NumberofStatutoryBusinessTrustsFormedorAcquired	8	Trust
CY2019Q3	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	70100000	USD
CY2018Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	61100000	USD
CY2019Q3	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	250000000.0	USD
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	1000000	shares
	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	2733603	shares
CY2019Q3	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	43.63
	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	42.25
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	-43700000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	-115600000	USD
	us-gaap	Dividends Dividends	25700000	USD
CY2019Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	33031	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	209183	shares
CY2019Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	46.33
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	45.78
CY2018Q3	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	18402	shares
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	201354	shares
CY2018Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	57.81
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	58.91
CY2019Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	2376000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	35599000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-19048000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	35599000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-3145000	USD
CY2019Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	26381000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	11594000	USD
CY2018Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-4203000	USD
CY2018Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-70363000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-71614000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-5454000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-66160000	USD
CY2018Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-70363000	USD
CY2018Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-51315000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-24502000	USD
CY2018Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-5454000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-33622000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	71597000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	2376000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	3152000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-7232000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	3152000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-7232000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-776000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	1778000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-776000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	1778000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5454000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5454000	USD
CY2019Q3	wal	Derivative Amountof Hedged Item Loans DerivativeAmountofHedgedItemLoans	591231000	USD
CY2019Q3	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	63216000	USD
CY2018Q4	wal	Derivative Amountof Hedged Item Loans DerivativeAmountofHedgedItemLoans	650428000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	23039000	USD
CY2019Q3	us-gaap	Derivative Amount Of Hedged Item DerivativeAmountOfHedgedItem	-318732000	USD
CY2019Q3	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	754000	USD
CY2018Q4	us-gaap	Derivative Amount Of Hedged Item DerivativeAmountOfHedgedItem	-299401000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	19691000	USD
CY2019Q3	wal	Collateral Netted Against Derivative Liabilities CollateralNettedAgainstDerivativeLiabilities	64000000.0	USD
CY2018Q4	wal	Collateral Netted Against Derivative Liabilities CollateralNettedAgainstDerivativeLiabilities	44900000	USD
CY2018Q3	wal	Collateral Netted Against Derivative Liabilities CollateralNettedAgainstDerivativeLiabilities	34700000	USD
CY2018Q3	wal	Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards DilutiveEffectOfStockOptionsRestrictedStockAndEquitySettledAwards	680000	shares
CY2019Q3	wal	Over Collateralization On Derivatives To Banks After Application Of Master Netting Agreements And Collateral OverCollateralizationOnDerivativesToBanksAfterApplicationOfMasterNettingAgreementsAndCollateral	31000000.0	USD
CY2019Q3	wal	Additional Collateral Amount AdditionalCollateralAmount	94900000	USD
CY2018Q4	wal	Over Collateralization On Derivatives To Banks After Application Of Master Netting Agreements And Collateral OverCollateralizationOnDerivativesToBanksAfterApplicationOfMasterNettingAgreementsAndCollateral	7600000	USD
CY2018Q3	wal	Over Collateralization On Derivatives To Banks After Application Of Master Netting Agreements And Collateral OverCollateralizationOnDerivativesToBanksAfterApplicationOfMasterNettingAgreementsAndCollateral	17700000	USD
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102041000	shares
CY2018Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104768000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	103024000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104664000	shares
CY2019Q3	wal	Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards DilutiveEffectOfStockOptionsRestrictedStockAndEquitySettledAwards	410000	shares
	wal	Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards DilutiveEffectOfStockOptionsRestrictedStockAndEquitySettledAwards	444000	shares
	wal	Dilutive Effect Of Stock Options Restricted Stock And Equity Settled Awards DilutiveEffectOfStockOptionsRestrictedStockAndEquitySettledAwards	734000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	102451000	shares
CY2018Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105448000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103468000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105398000	shares
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	127375000	USD
CY2018Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	111123000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	371107000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	316702000	USD
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.03
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.05
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.59
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.00
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1830
CY2018Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.0632
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1752
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1448
CY2019Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	3700000	USD
	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-28300000	USD
CY2019Q3	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	3700000	USD
CY2019Q3	us-gaap	Operating Loss Carryforwards Valuation Allowance OperatingLossCarryforwardsValuationAllowance	2400000	USD
CY2019Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	338600000	USD
CY2018Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	342400000	USD
CY2019Q3	us-gaap	Affordable Housing Program Obligation AffordableHousingProgramObligation	132300000	USD
CY2018Q4	us-gaap	Affordable Housing Program Obligation AffordableHousingProgramObligation	171700000	USD
CY2019Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	13000000.0	USD
CY2018Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	9000000.0	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	33600000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	26500000	USD
	us-gaap	Line Of Credit Facility Expiration Period LineOfCreditFacilityExpirationPeriod	P1Y
CY2019Q3	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	9860671000	USD
CY2018Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8184214000	USD
	wal	Maximum Loan To Value Ratio MaximumLoanToValueRatio	0.75
CY2019Q3	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.31
CY2018Q4	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.36
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	598000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-2028000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-6664000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	186000	USD
CY2019Q3	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	57521000	USD
CY2019Q3	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	63216000	USD
CY2019Q3	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	754000	USD
CY2018Q4	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	48684000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	23039000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	19691000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	600000	USD
CY2018Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-2000000.0	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-6700000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	200000	USD
CY2019Q3	wal	Impaired Financing Receivables With Norelated Allowance Balanceswith Chargeoffs ImpairedFinancingReceivablesWithNorelatedAllowanceBalanceswithChargeoffs	9600000	USD
CY2018Q4	wal	Impaired Financing Receivables With Norelated Allowance Balanceswith Chargeoffs ImpairedFinancingReceivablesWithNorelatedAllowanceBalanceswithChargeoffs	19400000	USD
CY2019Q3	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20800000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	1000000.0	USD
CY2018Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	299200000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	14500000	USD
CY2018Q4	wal	Other Assets Segment OtherAssetsSegment	974800000	USD
CY2018Q4	us-gaap	Assets Assets	23109500000	USD
CY2018Q4	us-gaap	Deposits Deposits	19177400000	USD
CY2018Q4	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	851500000	USD
CY2018Q4	wal	Other Liabilities Segment OtherLiabilitiesSegment	466900000	USD
CY2018Q4	us-gaap	Liabilities Liabilities	20495800000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710600000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	17557900000	USD
CY2018Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	17900000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	768439000	USD
CY2019Q3	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	5020200000	USD
CY2019Q3	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	15500000	USD
CY2019Q3	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	298000000.0	USD
CY2019Q3	wal	Other Assets Segment OtherAssetsSegment	1002700000	USD
CY2019Q3	us-gaap	Assets Assets	26324200000	USD
CY2019Q3	us-gaap	Deposits Deposits	22440800000	USD
CY2019Q3	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	388900000	USD
CY2019Q3	wal	Other Liabilities Segment OtherLiabilitiesSegment	571500000	USD
CY2019Q3	us-gaap	Liabilities Liabilities	23401200000	USD
CY2019Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	26324200000	USD
CY2019Q3	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	266422000	USD
CY2019Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	4000000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	262422000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	125955000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	155908000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28533000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	753939000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
	us-gaap	Noninterest Expense NoninterestExpense	353082000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	449926000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	78819000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
CY2018Q4	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	4259700000	USD
	wal	Othernoninterestincome Othernoninterestincome	187000	USD
CY2018Q3	wal	Success Fees SuccessFees	675000	USD
CY2018Q3	wal	Othernoninterestincome Othernoninterestincome	84000	USD
CY2018Q3	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	7860000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2613700000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	23109500000	USD
CY2018Q4	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2018Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	234038000	USD
CY2018Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6000000	USD
CY2018Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	228038000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	4418000	USD
CY2018Q3	us-gaap	Noninterest Expense NoninterestExpense	113841000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	118615000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7492000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	111123000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	672366000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17000000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	655366000	USD
	us-gaap	Noninterest Income NoninterestIncome	29505000	USD
	us-gaap	Noninterest Expense NoninterestExpense	314538000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	370333000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	53631000	USD
	us-gaap	Net Income Loss NetIncomeLoss	316702000	USD
CY2019Q3	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5888000	USD
CY2019Q3	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	1977000	USD
CY2019Q3	wal	Success Fees SuccessFees	605000	USD
CY2019Q3	wal	Othernoninterestincome Othernoninterestincome	80000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	8550000	USD
CY2019Q3	wal	Otherrevenue Otherrevenue	10891000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	17121000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	5830000	USD
	wal	Success Fees SuccessFees	1125000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	24263000	USD
	wal	Otherrevenue Otherrevenue	24806000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
CY2018Q3	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5267000	USD
CY2018Q3	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	1834000	USD
CY2018Q3	wal	Otherrevenue Otherrevenue	-3442000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	4418000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	16684000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	4990000	USD
	wal	Success Fees SuccessFees	2370000	USD
	wal	Othernoninterestincome Othernoninterestincome	497000	USD
	us-gaap	Noninterest Income NoninterestIncome	29505000	USD
CY2019Q3	us-gaap	Accounts Receivable Net AccountsReceivableNet	1500000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	24541000	USD
	wal	Otherrevenue Otherrevenue	4964000	USD
CY2018Q4	us-gaap	Accounts Receivable Net AccountsReceivableNet	1400000	USD

Files In Submission

Name	View Source	Status
0001212545-19-000115-index-headers.html	Edgar Link	pending
0001212545-19-000115-index.html	Edgar Link	pending
0001212545-19-000115.txt	Edgar Link	pending
0001212545-19-000115-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
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report.css	Edgar Link	pending
Show.js	Edgar Link	pending
wal-20190930.xsd	Edgar Link	pending
wal-20190930_cal.xml	Edgar Link	unprocessable
wal-20190930_def.xml	Edgar Link	unprocessable
wal-20190930_lab.xml	Edgar Link	unprocessable
wal-20190930_pre.xml	Edgar Link	unprocessable
wal930201910-q.htm	Edgar Link	pending
wal930201910-q_htm.xml	Edgar Link	completed
walex3119302019.htm	Edgar Link	pending
walex3129302019.htm	Edgar Link	pending
walex329302019.htm	Edgar Link	pending

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$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

2019 Q4 Form 10-Q Financial Statement

#000121254519000115 Filed on October 31, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL WESTERN ALLIANCE BANCORPORATION Stock $wal

2019 Q4 Form 10-Q Financial Statement

#000121254519000115 Filed on October 31, 2019

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal