$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

$wal Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000121254520000104 Filed on March 02, 2020

Income Statement

Concept	2019 Q4	2018 Q4	2018 Q3
Revenue	$315.4M	$282.0M	$265.2M
YoY Change	11.86%	23.42%	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	$3.800M	$3.700M
YoY Change	31.58%	11.76%	2.78%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$43.40M	$38.46M	$31.18M
YoY Change	12.86%	120.63%	91.83%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$154.3M	$140.0M	$118.6M
YoY Change	10.22%	12.61%	0.74%
Income Tax	$26.20M	$20.91M	$7.492M
% Of Pretax Income	16.98%	14.94%	6.32%
Net Earnings	$128.1M	$119.1M	$111.1M
YoY Change	7.57%	33.29%	34.14%
Net Earnings / Revenue	40.62%	42.23%	41.9%
Basic Earnings Per Share	$1.26	$1.14	$1.06
Diluted Earnings Per Share	$1.25	$1.13	$1.05
COMMON SHARES
Basic Shares Outstanding	102.6M shares	105.9M shares	104.8M shares
Diluted Shares Outstanding			105.4M shares

Balance Sheet

Concept	2019 Q4	2018 Q4	2018 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$434.6M	$498.6M	$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	$119.5M	$119.2M
YoY Change	5.29%	0.64%	-0.71%
Goodwill	$289.9M	$289.9M	$289.9M
YoY Change	0.0%	0.0%	0.0%
Intangibles	$7.713M	$9.260M	$9.658M
YoY Change	-16.71%	-14.68%	-14.24%
Long-Term Investments	$139.0M	$115.0M	$172.0M
YoY Change	20.87%
Other Assets	$18.00M	$32.00M	$43.00M
YoY Change	-43.75%	433.33%	-48.81%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$26.82B	$23.11B	$22.18B
YoY Change	16.06%	13.68%	11.31%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$78.00M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$491.0M	$0.00
YoY Change	-100.0%	25.9%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$78.00M	$22.00M	$21.00M
YoY Change	254.55%	-15.38%	-19.23%
LONG-TERM LIABILITIES
Long-Term Debt	$394.0M	$360.0M	$359.0M
YoY Change	9.44%	-53.06%	-3.75%
Other Long-Term Liabilities	$520.0M	$444.0M	$399.0M
YoY Change	17.12%	32.93%	-15.64%
Total Long-Term Liabilities	$914.0M	$804.0M	$758.0M
YoY Change	13.68%	-26.98%	-10.4%
TOTAL LIABILITIES
Total Short-Term Liabilities	$78.00M	$22.00M	$21.00M
Total Long-Term Liabilities	$914.0M	$804.0M	$758.0M
Total Liabilities	$23.81B	$20.50B	$19.69B
YoY Change	16.15%	13.24%	10.75%
SHAREHOLDERS EQUITY
Retained Earnings	$1.680B	$1.283B	$1.166B
YoY Change	31.0%	51.18%	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	$53.08M	$52.04M
YoY Change	18.12%	32.14%	30.07%
Treasury Stock Shares	2.004M shares
Shareholders Equity	$3.017B	$2.614B	$2.488B
YoY Change
Total Liabilities & Shareholders Equity	$26.82B	$23.11B	$22.18B
YoY Change	16.06%	13.68%	11.31%

Cashflow Statement

Concept	2019 Q4	2018 Q4	2018 Q3
OPERATING ACTIVITIES
Net Income	$128.1M	$119.1M	$111.1M
YoY Change	7.57%	33.29%	34.14%
Depreciation, Depletion And Amortization	$5.000M	$3.800M	$3.700M
YoY Change	31.58%	11.76%	2.78%
Cash From Operating Activities	$183.3M	$144.7M	$148.9M
YoY Change	26.68%	28.39%	55.59%
INVESTING ACTIVITIES
Capital Expenditures	-$19.80M	-$3.000M	-$6.500M
YoY Change	560.0%	130.77%	160.0%
Acquisitions
YoY Change
Other Investing Activities	-$928.0M	-$1.068B	-$696.6M
YoY Change	-13.13%	33.09%	-23.74%
Cash From Investing Activities	-$947.8M	-$1.071B	-$703.2M
YoY Change	-11.52%	33.25%	-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	724.6M	748.0M
YoY Change	-54.86%	58.35%	-13.43%
NET CHANGE
Cash From Operating Activities	183.3M	144.7M	148.9M
Cash From Investing Activities	-947.8M	-1.071B	-703.2M
Cash From Financing Activities	327.1M	724.6M	748.0M
Net Change In Cash	-437.4M	-201.9M	193.7M
YoY Change	116.64%	-13.57%	342.24%
FREE CASH FLOW
Cash From Operating Activities	$183.3M	$144.7M	$148.9M
Capital Expenditures	-$19.80M	-$3.000M	-$6.500M
Free Cash Flow	$203.1M	$147.7M	$155.4M
YoY Change	37.51%	29.56%	58.25%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2018Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	104949000	shares
CY2019Q1	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	102524000	shares
CY2017	us-gaap	Interest Expense Related Party InterestExpenseRelatedParty	200000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax	-3973000	USD
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CY2017	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	2220000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	-1857000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	3197000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	-79000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	24000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	138000	USD
CY2019	dei	Document Transition Report DocumentTransitionReport	false
CY2019	dei	Entity Registrant Name EntityRegistrantName	WESTERN ALLIANCE BANCORPORATION
CY2019	dei	Entity File Number EntityFileNumber	001-32550
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CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	5119000	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-3611000	USD
CY2017	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-1000	USD
CY2019	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	6156000	USD
CY2017	us-gaap	Labor And Related Expense LaborAndRelatedExpense	214344000	USD
CY2019	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	37009000	USD
CY2018	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	28722000	USD
CY2017	wal	Lendingrelatedfees Lendingrelatedfees	2212000	USD
CY2017	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	29814000	USD
CY2019	us-gaap	Occupancy Net OccupancyNet	32507000	USD
CY2019	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
CY2018	us-gaap	Occupancy Net OccupancyNet	29404000	USD
CY2018	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	-7656000	USD
CY2018	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	22295000	USD
CY2017	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	20346000	USD
CY2019	wal	Incomefrom Equity Investments IncomefromEquityInvestments	8290000	USD
CY2018	wal	Incomefrom Equity Investments IncomefromEquityInvestments	8595000	USD
CY2017	wal	Incomefrom Equity Investments IncomefromEquityInvestments	4496000	USD
CY2019	wal	Card Income CardIncome	6979000	USD
CY2018	wal	Card Income CardIncome	8009000	USD
CY2017	wal	Card Income CardIncome	6313000	USD
CY2019	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	4987000	USD
CY2018	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	4760000	USD
CY2017	us-gaap	Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet	3536000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3901000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3946000	USD
CY2017	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3861000	USD
CY2019	wal	Lendingrelatedfees Lendingrelatedfees	3158000	USD
CY2018	wal	Lendingrelatedfees Lendingrelatedfees	4340000	USD
CY2018	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	2438000	USD
CY2017	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	2238000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	65095000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	43116000	USD
CY2017	us-gaap	Noninterest Income NoninterestIncome	45344000	USD
CY2019	us-gaap	Labor And Related Expense LaborAndRelatedExpense	279274000	USD
CY2018	us-gaap	Labor And Related Expense LaborAndRelatedExpense	253238000	USD
CY2017	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	19225000	USD
CY2019	us-gaap	General Insurance Expense GeneralInsuranceExpense	11924000	USD
CY2018	us-gaap	General Insurance Expense GeneralInsuranceExpense	14005000	USD
CY2019	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	7571000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	33247000	USD
CY2018	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	4578000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	38470000	USD
CY2018	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	22716000	USD
CY2017	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	4617000	USD
CY2017	us-gaap	General Insurance Expense GeneralInsuranceExpense	14042000	USD
CY2019	us-gaap	Marketing Expense MarketingExpense	4199000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1594000	USD
CY2019	us-gaap	Business Development BusinessDevelopment	7043000	USD
CY2017	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-80000	USD
CY2018	us-gaap	Business Development BusinessDevelopment	5960000	USD
CY2017	us-gaap	Business Development BusinessDevelopment	6128000	USD
CY2018	us-gaap	Marketing Expense MarketingExpense	3770000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	2074000	USD
CY2017	us-gaap	Marketing Expense MarketingExpense	3804000	USD
CY2019	wal	Cardexpense Cardexpense	2346000	USD
CY2019	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	3818000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	482781000	USD
CY2018	wal	Cardexpense Cardexpense	4301000	USD
CY2017	wal	Cardexpense Cardexpense	3413000	USD
CY2018	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	9000	USD
CY2017	us-gaap	Other Noninterest Expense OtherNoninterestExpense	25969000	USD
CY2017	us-gaap	Noninterest Expense NoninterestExpense	360941000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	604226000	USD
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	104997000	shares
CY2019	us-gaap	Net Income Loss NetIncomeLoss	499171000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	435788000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	325492000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	71222000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-40808000	USD
CY2017	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	6334000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	412000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	77000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	425667000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-264000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-9804000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	5693000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	510328000	USD
CY2017	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	451817000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	105055000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	74540000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	126325000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	499171000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	435788000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	325492000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.86
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.16
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.12
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.84
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.14
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.10
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102667000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104669000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104179000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103133000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105370000	shares
CY2017	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3604000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5773000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1444000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	58630000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-29419000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	1550000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	557801000	USD
CY2018	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	35688000	USD
CY2017	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-1000	USD
CY2019	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	690000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	406369000	USD
CY2017	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	327042000	USD
CY2018	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	-7656000	USD
CY2016Q4	us-gaap	Stockholders Equity StockholdersEquity	1891529000	USD
CY2017Q1	us-gaap	Stockholders Equity StockholdersEquity	1892067000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	325492000	USD
CY2017	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	846000	USD
CY2017	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	23554000	USD
CY2018Q1	us-gaap	Stockholders Equity StockholdersEquity	2229698000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	435788000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	554000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	25711000	USD
CY2018	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	12910000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	1550000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	2229698000	USD
CY2017	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	13811000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-29419000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2613734000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	499171000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	80000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	26238000	USD
CY2019	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	9645000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	120131000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	51329000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	58630000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3016748000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	499171000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	435788000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	325492000	USD
CY2019	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	18500000	USD
CY2018	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	23000000	USD
CY2017	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17250000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	18457000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	14319000	USD
CY2017	us-gaap	Depreciation And Amortization DepreciationAndAmortization	13393000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	26238000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	25711000	USD
CY2017	us-gaap	Share Based Compensation ShareBasedCompensation	23554000	USD
CY2019	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-5129000	USD
CY2018	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-16709000	USD
CY2017	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	88471000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-17095000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-14247000	USD
CY2017	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-16938000	USD
CY2019	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	41501000	USD
CY2018	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	35898000	USD
CY2017	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	25355000	USD
CY2019	us-gaap	Operating Lease Expense OperatingLeaseExpense	10458000	USD
CY2018	us-gaap	Operating Lease Expense OperatingLeaseExpense	0	USD
CY2017	us-gaap	Operating Lease Expense OperatingLeaseExpense	0	USD
CY2019	wal	Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitionsof Loans AccretionAndAmortizationFairMarketValueAdjustmentsRelatingToAcquisitionsofLoans	12678000	USD
CY2018	wal	Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitionsof Loans AccretionAndAmortizationFairMarketValueAdjustmentsRelatingToAcquisitionsofLoans	18565000	USD
CY2017	wal	Accretion And Amortization Fair Market Value Adjustments Relating To Acquisitionsof Loans AccretionAndAmortizationFairMarketValueAdjustmentsRelatingToAcquisitionsofLoans	28235000	USD
CY2019	wal	Accretionand Amortization Fair Market Value Adjustments Relatingto Acquisitionsof Other Assetsand Liabilities AccretionandAmortizationFairMarketValueAdjustmentsRelatingtoAcquisitionsofOtherAssetsandLiabilities	-1857000	USD
CY2018	wal	Accretionand Amortization Fair Market Value Adjustments Relatingto Acquisitionsof Other Assetsand Liabilities AccretionandAmortizationFairMarketValueAdjustmentsRelatingtoAcquisitionsofOtherAssetsandLiabilities	-1904000	USD
CY2017	wal	Accretionand Amortization Fair Market Value Adjustments Relatingto Acquisitionsof Other Assetsand Liabilities AccretionandAmortizationFairMarketValueAdjustmentsRelatingtoAcquisitionsofOtherAssetsandLiabilities	-2385000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3901000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3946000	USD
CY2018	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	2638000	USD
CY2017	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	945000	USD
CY2019	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	604000	USD
CY2018	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	1214000	USD
CY2017	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	228000	USD
CY2017	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	2343000	USD
CY2019	wal	Valuation Adjustments Of Other Repossessed Assets Net ValuationAdjustmentsOfOtherRepossessedAssetsNet	-4144000	USD
CY2017	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	3861000	USD
CY2018	wal	Valuation Adjustments Of Other Repossessed Assets Net ValuationAdjustmentsOfOtherRepossessedAssetsNet	-1267000	USD
CY2017	wal	Valuation Adjustments Of Other Repossessed Assets Net ValuationAdjustmentsOfOtherRepossessedAssetsNet	-120000	USD
CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	5119000	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-3611000	USD
CY2019	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	3152000	USD
CY2019	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-278000	USD
CY2017	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	169400000	USD
CY2018	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	-577000	USD
CY2017	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	0	USD
CY2018	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	44000	USD
CY2017	us-gaap	Gain Loss On Disposition Of Assets GainLossOnDispositionOfAssets	-28000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-111346000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-20687000	USD
CY2017	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	93564000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	717772000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	540972000	USD
CY2017	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	383811000	USD
CY2019	wal	Proceeds From Sale Of Securities Measured At Fair Value ProceedsFromSaleOfSecuritiesMeasuredAtFairValue	0	USD
CY2018	wal	Proceeds From Sale Of Securities Measured At Fair Value ProceedsFromSaleOfSecuritiesMeasuredAtFairValue	0	USD
CY2017	wal	Proceeds From Sale Of Securities Measured At Fair Value ProceedsFromSaleOfSecuritiesMeasuredAtFairValue	994000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	927589000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	520734000	USD
CY2017	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	1429434000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	785659000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	425151000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	430934000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	150377000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	154434000	USD
CY2017	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	110104000	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	131384000	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	56575000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	21594000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	8987000	USD
CY2017	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	6174000	USD
CY2019	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	10000000	USD
CY2018	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
CY2017	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
CY2019	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	32725000	USD
CY2018	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	71728000	USD
CY2017	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	0	USD
CY2019	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	14598000	USD
CY2019	wal	Proceedsfrom Saleof Equitysecurities Fvni ProceedsfromSaleofEquitysecuritiesFVNI	0	USD
CY2018	wal	Proceedsfrom Saleof Equitysecurities Fvni ProceedsfromSaleofEquitysecuritiesFVNI	48639000	USD
CY2017	wal	Proceedsfrom Saleof Equitysecurities Fvni ProceedsfromSaleofEquitysecuritiesFVNI	0	USD
CY2019	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	141668000	USD
CY2018	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	109598000	USD
CY2017	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	38098000	USD
CY2019	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	8688000	USD
CY2018	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	4129000	USD
CY2017	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	5819000	USD
CY2019	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	7000	USD
CY2018	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	-7000	USD
CY2017	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	0	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1655000	USD
CY2017	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	607000	USD
CY2019	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	377000	USD
CY2018	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	347000	USD
CY2017	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	535000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	3429014000	USD
CY2018	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	2586703000	USD
CY2017	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	1873387000	USD
CY2019	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	35148000	USD
CY2018	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	11313000	USD
CY2017	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	8862000	USD
CY2019	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	1325000	USD
CY2018	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	9412000	USD
CY2017	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	21195000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-3723033000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-2713433000	USD
CY2017	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-2955527000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	3619046000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	2204915000	USD
CY2017	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	2422669000	USD
CY2019	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-496736000	USD
CY2018	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	97394000	USD
CY2017	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	294289000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	80000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	554000	USD
CY2017	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	846000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	9645000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	12910000	USD
CY2017	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	13811000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	120131000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	35688000	USD
CY2017	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	51329000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	0	USD
CY2017	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	0	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2941285000	USD
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	416768000	USD
CY2019	us-gaap	Interest Paid InterestPaid	180436000	USD
CY2018	us-gaap	Interest Paid InterestPaid	113507000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2254265000	USD
CY2017	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2703993000	USD
CY2019	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	-63976000	USD
CY2018	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	81804000	USD
CY2017	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	132277000	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
CY2016Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	284491000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	434596000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	498572000	USD
CY2017	us-gaap	Interest Paid InterestPaid	59838000	USD
CY2019	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-23403000	USD
CY2018	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	18760000	USD
CY2017	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	99430000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	898000	USD
CY2018	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	5744000	USD
CY2017	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	1812000	USD
CY2019	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>
CY2019	wal	Number Of Unconsolidated Subsidiaries NumberOfUnconsolidatedSubsidiaries	8	Subsidiary
CY2019	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>
CY2019Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	359000000.0	USD
CY2018Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	358700000	USD
CY2019Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	19870000	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3346310000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	135319000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	485107000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	31303000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	149000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	516261000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3317928000	USD
CY2019Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	48252000	USD
CY2019Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	3881000	USD
CY2019Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	499000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	138701000	USD
CY2018Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	302905000	USD
CY2018Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	3163000	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	Available For Sale Securities AvailableForSaleSecurities	3276988000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	118164000	USD
CY2018Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	148000	USD
CY2018Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	3251000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	115061000	USD
CY2019Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	158	positions
CY2018Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	373	positions
CY2019	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
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	4023000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	799113000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	15847000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	585688000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	19870000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	1384801000	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
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	7330000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	7384000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	17414000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	17947000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	460363000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	490930000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	485107000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	516261000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	999000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	999000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	14765000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	14971000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	149236000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	144996000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	521287000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	549804000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost	2631641000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	2635540000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3317928000	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3346310000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	-7992000	USD
CY2017	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	3200000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	7700000	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	0	USD
CY2017	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	0	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	7992000	USD
CY2017	us-gaap	Equity Securities Fv Ni Realized Loss EquitySecuritiesFvNiRealizedLoss	0	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3346310000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	138701000	USD
CY2018Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3276988000	USD
CY2018Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	115061000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	962500000	USD
CY2018Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	788400000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3152000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	8074000	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3204000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	7738000	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	861000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	3152000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	336000	USD
CY2017	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	2343000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	0	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	21065187000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	36306000	USD
CY2019Q4	wal	Credit Markon Acquired Loans CreditMarkonAcquiredLoans	6500000	USD
CY2018Q4	wal	Credit Markon Acquired Loans CreditMarkonAcquiredLoans	14600000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	21800000	USD
CY2018Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	167797000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	152717000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	20933696000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	17557912000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	47700000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	36300000	USD
CY2019Q4	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	29900000	USD
CY2018Q4	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	2000000.0	USD
CY2019Q4	wal	Interest Rate Markson Acquired Loans InterestRateMarksonAcquiredLoans	3800000	USD
CY2018Q4	wal	Interest Rate Markson Acquired Loans InterestRateMarksonAcquiredLoans	7100000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	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
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	55968000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	27746000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	594000	USD
CY2019	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	2200000	USD
CY2018	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	2300000	USD
CY2017	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	2400000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	21065187000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	2776000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	681000	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
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20979000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	986000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	95324000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	111266000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	116303000	USD
CY2018Q4	us-gaap	Impaired Financing Receivable Recorded Investment ImpairedFinancingReceivableRecordedInvestment	112252000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	116303000	USD
CY2018Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	112252000	USD
CY2019	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	121287000	USD
CY2018	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	104825000	USD
CY2017	us-gaap	Impaired Financing Receivable Average Recorded Investment ImpairedFinancingReceivableAverageRecordedInvestment	104866000	USD
CY2019	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	5012000	USD
CY2018	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	4490000	USD
CY2017	us-gaap	Impaired Financing Receivable Interest Income Accrual Method ImpairedFinancingReceivableInterestIncomeAccrualMethod	4046000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	55968000	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	27746000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2018Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	594000	USD
CY2019Q4	wal	Non Performing Loans NonPerformingLoans	84324000	USD
CY2018Q4	wal	Non Performing Loans NonPerformingLoans	64798000	USD
CY2019Q4	us-gaap	Foreclosed Assets ForeclosedAssets	13850000	USD
CY2018Q4	us-gaap	Foreclosed Assets ForeclosedAssets	17924000	USD
CY2019Q4	wal	Non Performing Assets NonPerformingAssets	98174000	USD
CY2018Q4	wal	Non Performing Assets NonPerformingAssets	82722000	USD
CY2016Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	124704000	USD
CY2017	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	11004000	USD
CY2017	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	9100000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6087000	USD
CY2016Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	15177000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Additions CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAdditions	0	USD
CY2019	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsFromNonaccretableDifference	0	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Reclassifications From Nonaccretable Difference CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldReclassificationsFromNonaccretableDifference	2086000	USD
CY2019	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	570000	USD
CY2018	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	1018000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Accretion CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldAccretion	2797000	USD
CY2017	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield Disposals Of Loans CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYieldDisposalsOfLoans	5142000	USD
CY2017Q4	us-gaap	Certain Loans Acquired In Transfer Not Accounted For As Debt Securities Accretable Yield CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAccretableYield	9324000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	152717000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	9122000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	5702000	USD
CY2019	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	18500000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	167797000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	140050000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	16420000	USD
CY2018	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	23000000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	152717000	USD
CY2017	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17250000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	140050000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	20979000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Recorded Investment ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment	95324000	USD
CY2019Q4	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	116303000	USD
CY2019Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	20932161000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance	24055000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance	99440000	USD
CY2019Q4	wal	Impaired Financing Receivable Unpaid Principal Balance Individually Evaluated For Impairment ImpairedFinancingReceivableUnpaidPrincipalBalanceIndividuallyEvaluatedForImpairment	123495000	USD
CY2019Q4	wal	Financing Receivable Unpaid Principal Balance Collectively Evaluated For Impairment FinancingReceivableUnpaidPrincipalBalanceCollectivelyEvaluatedForImpairment	20921137000	USD
CY2019Q4	wal	Financing Receivable Unpaid Principal Balance FinancingReceivableUnpaidPrincipalBalance	21108472000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable Related Allowance ImpairedFinancingReceivableRelatedAllowance	2776000	USD
CY2019Q4	wal	Impaired Financing Receivable With No Related Allowance ImpairedFinancingReceivableWithNoRelatedAllowance	0	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	2776000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	164923000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	167797000	USD
CY2018Q4	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	17514822000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	17710629000	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	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	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	112252000	USD
CY2017	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	6628000	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
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	9
CY2019	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	42045000	USD
CY2019	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Principal Forgiveness FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToPrincipalForgiveness	0	USD
CY2019	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Interest Concessions FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToInterestConcessions	0	USD
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	42045000	USD
CY2019	wal	Financing Receivable Waived Fees And Other Expenses FinancingReceivableWaivedFeesAndOtherExpenses	0	USD
CY2018	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	12
CY2018	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	35426000	USD
CY2018	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Principal Forgiveness FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToPrincipalForgiveness	0	USD
CY2018	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Interest Concessions FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToInterestConcessions	0	USD
CY2018	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	35426000	USD
CY2018	wal	Financing Receivable Waived Fees And Other Expenses FinancingReceivableWaivedFeesAndOtherExpenses	0	USD
CY2017	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	15
CY2017	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	6628000	USD
CY2017	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Principal Forgiveness FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToPrincipalForgiveness	0	USD
CY2017	wal	Financing Receivables Impaired Troubled Debt Restructuring Write Down Due To Interest Concessions FinancingReceivablesImpairedTroubledDebtRestructuringWriteDownDueToInterestConcessions	0	USD
CY2017	wal	Financing Receivable Waived Fees And Other Expenses FinancingReceivableWaivedFeesAndOtherExpenses	0	USD
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	2
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	371000	USD
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2017	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	6
CY2017	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	1697000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	200000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	1500000	USD
CY2019	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	2533407000	USD
CY2018	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	1600818000	USD
CY2019	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	98963000	USD
CY2018	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	66477000	USD
CY2019	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	690000	USD
CY2018	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	2638000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	43681000	USD
CY2019Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	91574000	USD
CY2018Q4	us-gaap	Buildings And Improvements Gross BuildingsAndImprovementsGross	89930000	USD
CY2019Q4	us-gaap	Land And Land Improvements LandAndLandImprovements	32954000	USD
CY2018Q4	us-gaap	Land And Land Improvements LandAndLandImprovements	32954000	USD
CY2019Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	53621000	USD
CY2018Q4	us-gaap	Furniture And Fixtures Gross FurnitureAndFixturesGross	42729000	USD
CY2019Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	28477000	USD
CY2018Q4	us-gaap	Leasehold Improvements Gross LeaseholdImprovementsGross	25919000	USD
CY2019Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	10449000	USD
CY2018Q4	us-gaap	Construction In Progress Gross ConstructionInProgressGross	6302000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	217075000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	197834000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	91237000	USD
CY2018Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	78360000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	125838000	USD
CY2018Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	119474000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	72600000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	78100000	USD
CY2019Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0308
CY2019Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P8Y4M24D
CY2019Q4	us-gaap	Goodwill Goodwill	289900000	USD
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	12435000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	12369000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	10413000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	9224000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	9060000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	9007000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	40072000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	90145000	USD
CY2019Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	12033000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	78112000	USD
CY2019Q4	wal	Lesseeoperatingleaseleasesnotyetcommencedaggregatedcommitment Lesseeoperatingleaseleasesnotyetcommencedaggregatedcommitment	3100000	USD
CY2019	us-gaap	Lease Cost LeaseCost	12900000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	4000000.0	USD
CY2018	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	11000000.0	USD
CY2017	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	10400000	USD
CY2019Q4	wal	Indefinite Lived Trade Name Gross IndefiniteLivedTradeNameGross	350000	USD
CY2019Q4	wal	Trade Name Impaired Accumulated Impairment Loss TradeNameImpairedAccumulatedImpairmentLoss	0	USD
CY2019Q4	us-gaap	Indefinite Lived Trade Names IndefiniteLivedTradeNames	350000	USD
CY2018Q4	wal	Indefinite Lived Trade Name Gross IndefiniteLivedTradeNameGross	350000	USD
CY2018Q4	wal	Trade Name Impaired Accumulated Impairment Loss TradeNameImpairedAccumulatedImpairmentLoss	0	USD
CY2018Q4	us-gaap	Indefinite Lived Trade Names IndefiniteLivedTradeNames	350000	USD
CY2017	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	2100000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1600000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1500000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	7953000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	3502000	USD
CY2019Q4	wal	Deposits Ics DepositsICS	661800000	USD
CY2018Q4	wal	Deposits Ics DepositsICS	706900000	USD
CY2019	wal	Depositscostsdepositswithearningscredits Depositscostsdepositswithearningscredits	30500000	USD
CY2018	wal	Depositscostsdepositswithearningscredits Depositscostsdepositswithearningscredits	18000000.0	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	1494000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	1433000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	1364000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	1289000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	1206000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense After Year Five FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive	577000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	7363000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	8537905000	USD
CY2018Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	7456141000	USD
CY2019Q4	us-gaap	Interest Bearing Domestic Deposit Demand InterestBearingDomesticDepositDemand	2760865000	USD
CY2018Q4	us-gaap	Interest Bearing Domestic Deposit Demand InterestBearingDomesticDepositDemand	2555609000	USD
CY2019Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	9120747000	USD
CY2018Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	7330709000	USD
CY2019Q4	wal	Time Deposits250000ormore TimeDeposits250000ormore	1426133000	USD
CY2018Q4	wal	Time Deposits250000ormore TimeDeposits250000ormore	1009900000	USD
CY2019Q4	wal	Time Deposits Lessthan250000 TimeDepositsLessthan250000	950843000	USD
CY2018Q4	wal	Time Deposits Lessthan250000 TimeDepositsLessthan250000	825088000	USD
CY2019Q4	us-gaap	Deposits Deposits	22796493000	USD
CY2018Q4	us-gaap	Deposits Deposits	19177447000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	2259182000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	105237000	USD
CY2019Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	1102000	USD
CY2019Q4	us-gaap	Time Deposits TimeDeposits	2376976000	USD
CY2019Q4	wal	Certificatesof Deposit Cdars CertificatesofDepositCDARS	407700000	USD
CY2018Q4	wal	Certificatesof Deposit Cdars CertificatesofDepositCDARS	322900000	USD
CY2018Q4	us-gaap	Deposits Wholesale DepositsWholesale	718200000	USD
CY2019Q4	us-gaap	Deposits Wholesale DepositsWholesale	1100000000	USD
CY2019Q4	wal	Noninterestbearingdepositearningscredit Noninterestbearingdepositearningscredit	3100000000	USD
CY2018Q4	wal	Noninterestbearingdepositearningscredit Noninterestbearingdepositearningscredit	2300000000	USD
CY2019Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	256000000	USD
CY2019Q4	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	USD
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	0	USD
CY2018Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	491000000	USD
CY2019Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2018Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	256000000.0	USD
CY2019Q4	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
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	16700000	USD
CY2018Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	22400000	USD
CY2019Q4	us-gaap	Subordinated Debt SubordinatedDebt	319200000	USD
CY2018Q4	us-gaap	Subordinated Debt SubordinatedDebt	299400000	USD
CY2019	wal	Numberof Statutory Business Trusts Formedor Acquired NumberofStatutoryBusinessTrustsFormedorAcquired	8	Trust
CY2019Q4	wal	Unrealizedgainorlossonjuniorsubordinateddebtcarriedatfairvalue Unrealizedgainorlossonjuniorsubordinateddebtcarriedatfairvalue	-4812000	USD
CY2018Q4	wal	Unrealizedgainorlossonjuniorsubordinateddebtcarriedatfairvalue Unrealizedgainorlossonjuniorsubordinateddebtcarriedatfairvalue	-17812000	USD
CY2019Q4	wal	Business Combination Fair Market Value Adjustmenton Junior Subordinated Debenture Owedto Unconsolidated Subsidiary Trust BusinessCombinationFairMarketValueAdjustmentonJuniorSubordinatedDebentureOwedtoUnconsolidatedSubsidiaryTrust	-4845000	USD
CY2018Q4	wal	Business Combination Fair Market Value Adjustmenton Junior Subordinated Debenture Owedto Unconsolidated Subsidiary Trust BusinessCombinationFairMarketValueAdjustmentonJuniorSubordinatedDebentureOwedtoUnconsolidatedSubsidiaryTrust	-5155000	USD
CY2019Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	74367000	USD
CY2018Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	61057000	USD
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized	10500000	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant	2900000	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	32.31
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	114000	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	50.80
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod	63000	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue	43.62
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	960000	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	49.98
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	1027000	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	47.53
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	46.04
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	36.96
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	516000	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue	39.60
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	477000	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	1027000	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue	47.53
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber	1142000	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod	425000	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	58.02
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	469000	shares
CY2019Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Share Based Awards Other Than Options EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions	23000000.0	USD
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Weighted Average Remaining Contractual Terms ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms	P1Y7M13D
CY2018Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	250000000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	2822402	shares
	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	42.53
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	120100000	USD
CY2020Q4	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	250000000.0	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.25
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	51300000	USD
CY2019	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	210657	shares
CY2019	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	45.80
CY2018	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	223125	shares
CY2018	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	57.88
CY2017	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	269865	shares
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	578063000	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	53292000	USD
CY2017	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	51.16
CY2016Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-4695000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	2994000	USD
CY2017	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	1444000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	1550000	USD
CY2017Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-3145000	USD
CY2018Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-4203000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-35192000	USD
CY2018	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-5773000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-29419000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-33622000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	61006000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	2376000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	58630000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	25008000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	3152000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-7656000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	2343000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-776000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	1883000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	-5773000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1444000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	650428000	USD
CY2018Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	23039000	USD
CY2019Q4	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	-319197000	USD
CY2019Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	401000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	-299401000	USD
CY2018Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	19691000	USD
CY2019Q4	us-gaap	Derivative Fair Value Amount Offset Against Collateral Net DerivativeFairValueAmountOffsetAgainstCollateralNet	55500000	USD
CY2018Q4	us-gaap	Derivative Fair Value Amount Offset Against Collateral Net DerivativeFairValueAmountOffsetAgainstCollateralNet	44900000	USD
CY2017Q4	us-gaap	Derivative Fair Value Amount Offset Against Collateral Net DerivativeFairValueAmountOffsetAgainstCollateralNet	53600000	USD
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	29200000	USD
CY2019Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	84700000	USD
CY2018Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	7600000	USD
CY2017Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	25000000.0	USD
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102667000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104669000	shares
CY2017	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	104179000	shares
CY2019	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	466000	shares
CY2018	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	701000	shares
CY2017	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	818000	shares
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	435788000	USD
CY2017	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	325492000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.86
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.16
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	105370000	shares
CY2017	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	104997000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103133000	shares
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	499171000	USD
CY2017	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.12
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.84
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.14
CY2017	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.10
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	110184000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	91249000	USD
CY2017	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	37854000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-5129000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-16709000	USD
CY2017	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	88471000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	105055000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	74540000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	126325000	USD
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	126888000	USD
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	107169000	USD
CY2017	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	158136000	USD
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	11004000	USD
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	9015000	USD
CY2017	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	9765000	USD
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	19527000	USD
CY2018	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	-18322000	USD
CY2017	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	26403000	USD
CY2019	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2018	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	0	USD
CY2017	us-gaap	Income Tax Reconciliation Change In Enacted Tax Rate IncomeTaxReconciliationChangeInEnactedTaxRate	10411000	USD
CY2019	wal	Effective Income Tax Rate Reconciliation No Land Other Carryback Amount EffectiveIncomeTaxRateReconciliationNOLandOtherCarrybackAmount	0	USD
CY2018	wal	Effective Income Tax Rate Reconciliation No Land Other Carryback Amount EffectiveIncomeTaxRateReconciliationNOLandOtherCarrybackAmount	-15341000	USD
CY2017	wal	Effective Income Tax Rate Reconciliation No Land Other Carryback Amount EffectiveIncomeTaxRateReconciliationNOLandOtherCarrybackAmount	0	USD
CY2019	wal	Effective Income Tax Reconciliation Excise Tax EffectiveIncomeTaxReconciliationExciseTax	0	USD
CY2018	wal	Effective Income Tax Reconciliation Excise Tax EffectiveIncomeTaxReconciliationExciseTax	-137000	USD
CY2017	wal	Effective Income Tax Reconciliation Excise Tax EffectiveIncomeTaxReconciliationExciseTax	9689000	USD
CY2019	wal	Income Tax Reconciliation Low Income Housing And Other Tax Credits IncomeTaxReconciliationLowIncomeHousingAndOtherTaxCredits	-15000000	USD
CY2018	wal	Income Tax Reconciliation Low Income Housing And Other Tax Credits IncomeTaxReconciliationLowIncomeHousingAndOtherTaxCredits	-6673000	USD
CY2017	wal	Income Tax Reconciliation Low Income Housing And Other Tax Credits IncomeTaxReconciliationLowIncomeHousingAndOtherTaxCredits	-7361000	USD
CY2019	wal	Income Tax Reconciliation Tax On Earnings Other Than Statutory Tax Rate IncomeTaxReconciliationTaxOnEarningsOtherThanStatutoryTaxRate	1690000	USD
CY2018	wal	Income Tax Reconciliation Tax On Earnings Other Than Statutory Tax Rate IncomeTaxReconciliationTaxOnEarningsOtherThanStatutoryTaxRate	-1171000	USD
CY2017	wal	Income Tax Reconciliation Tax On Earnings Other Than Statutory Tax Rate IncomeTaxReconciliationTaxOnEarningsOtherThanStatutoryTaxRate	-7090000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	105055000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	74540000	USD
CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	126325000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1739
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1461
CY2017	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.2796
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	44809000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Provision For Loan Losses DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsProvisionForLoanLosses	42833000	USD
CY2019Q4	wal	Deferred Tax Assets Leasing Arrangements DeferredTaxAssetsLeasingArrangements	20264000	USD
CY2018Q4	wal	Deferred Tax Assets Leasing Arrangements DeferredTaxAssetsLeasingArrangements	0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	7351000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	8718000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	5619000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	6255000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Unrealized Losses On Availablefor Sale Securities Gross DeferredTaxAssetsUnrealizedLossesOnAvailableforSaleSecuritiesGross	16047000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	19361000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	20687000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	97404000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	94540000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	2373000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	97404000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Net DeferredTaxAssetsNet	92167000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	18823000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Leasing Arrangements DeferredTaxLiabilitiesLeasingArrangements	0	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other Comprehensive Income DeferredTaxLiabilitiesOtherComprehensiveIncome	7264000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other Comprehensive Income DeferredTaxLiabilitiesOtherComprehensiveIncome	0	USD
CY2019Q4	wal	Deferred Tax Liabilities Unrealized Gainson Debt Instruments Measuredat Fair Value DeferredTaxLiabilitiesUnrealizedGainsonDebtInstrumentsMeasuredatFairValue	-1229000	USD
CY2018Q4	wal	Deferred Tax Liabilities Unrealized Gainson Debt Instruments Measuredat Fair Value DeferredTaxLiabilitiesUnrealizedGainsonDebtInstrumentsMeasuredatFairValue	-5833000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Financing Arrangements DeferredTaxLiabilitiesFinancingArrangements	10789000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Financing Arrangements DeferredTaxLiabilitiesFinancingArrangements	9528000	USD
CY2018Q4	wal	Deferred Tax Liabilities Insurance Premiums DeferredTaxLiabilitiesInsurancePremiums	-6527000	USD
CY2019Q4	wal	Deferred Tax Liabilities Insurance Premiums DeferredTaxLiabilitiesInsurancePremiums	-4514000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	8372000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	1201000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	-14890000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Deferred Expense Reserves And Accruals DeferredTaxLiabilitiesDeferredExpenseReservesAndAccruals	-31592000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	-6792000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Tax Deferred Income DeferredTaxLiabilitiesTaxDeferredIncome	-1624000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	6706000	USD
CY2018Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	3872000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	79379000	USD
CY2018Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	60177000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	18025000	USD
CY2018Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	31990000	USD
CY2019	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	-14000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	18000000.0	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	18000000.0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Settlements With Taxing Authorities UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities	307000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Reductions Resulting From Lapse Of Applicable Statute Of Limitations UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1739000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	484000	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	1100000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits That Would Impact Effective Tax Rate UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate	300000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2018Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	2400000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	1255000	USD
CY2018	us-gaap	Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2018	us-gaap	Unrecognized Tax Benefits Decreases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsDecreasesResultingFromPriorPeriodTaxPositions	247000	USD
CY2018Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	484000	USD
CY2017Q4	us-gaap	Unrecognized Tax Benefits UnrecognizedTaxBenefits	1038000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Increases Resulting From Prior Period Tax Positions UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions	0	USD
CY2019Q4	us-gaap	Decrease In Unrecognized Tax Benefits Is Reasonably Possible DecreaseInUnrecognizedTaxBenefitsIsReasonablyPossible	100000	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesExpense	0	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Income Tax Penalties Accrued UnrecognizedTaxBenefitsIncomeTaxPenaltiesAccrued	0.1	USD
CY2019Q4	us-gaap	Unrecognized Tax Benefits Interest On Income Taxes Accrued UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued	0	USD
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CY2019Q4	us-gaap	Variable Interest Entity Nonconsolidated Carrying Amount Assets VariableInterestEntityNonconsolidatedCarryingAmountAssets	409400000	USD
CY2018Q4	us-gaap	Variable Interest Entity Nonconsolidated Carrying Amount Assets VariableInterestEntityNonconsolidatedCarryingAmountAssets	369600000	USD
CY2019Q4	us-gaap	Variable Interest Entity Nonconsolidated Carrying Amount Liabilities VariableInterestEntityNonconsolidatedCarryingAmountLiabilities	191000000.0	USD
CY2018Q4	us-gaap	Variable Interest Entity Nonconsolidated Carrying Amount Liabilities VariableInterestEntityNonconsolidatedCarryingAmountLiabilities	196300000	USD
CY2019	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	41500000	USD
CY2018	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	35900000	USD
CY2017	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	25400000	USD
CY2019	us-gaap	Line Of Credit Facility Expiration Period LineOfCreditFacilityExpirationPeriod	P1Y
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CY2019Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8827108000	USD
CY2018Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8184214000	USD
CY2019Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8827108000	USD
CY2019Q4	us-gaap	Other Commitment Due In Next Twelve Months OtherCommitmentDueInNextTwelveMonths	3332587000	USD
CY2019Q4	us-gaap	Other Commitment Due In Second And Third Year OtherCommitmentDueInSecondAndThirdYear	3189634000	USD
CY2019Q4	us-gaap	Other Commitment Due In Fourth And Fifth Year OtherCommitmentDueInFourthAndFifthYear	1300123000	USD
CY2019Q4	us-gaap	Other Commitment Due After Fifth Year OtherCommitmentDueAfterFifthYear	1004764000	USD
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CY2019Q4	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.31
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CY2018	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	5693000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3604000	USD
CY2019Q4	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	61685000	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	53292000	USD
CY2019Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	401000	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
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CY2018	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	5700000	USD
CY2017	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3600000	USD
CY2019Q4	wal	Impaired Financing Receivables With Norelated Allowance Balanceswith Chargeoffs ImpairedFinancingReceivablesWithNorelatedAllowanceBalanceswithChargeoffs	3300000	USD
CY2018Q4	wal	Impaired Financing Receivables With Norelated Allowance Balanceswith Chargeoffs ImpairedFinancingReceivablesWithNorelatedAllowanceBalanceswithChargeoffs	19400000	USD
CY2019Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	21000000.0	USD
CY2018Q4	us-gaap	Impaired Financing Receivable With Related Allowance Recorded Investment ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment	1000000.0	USD
CY2019Q4	us-gaap	Capital Required To Be Well Capitalized To Risk Weighted Assets CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.100
CY2019Q4	us-gaap	Tier One Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.080
CY2019Q4	us-gaap	Tier One Leverage Capital Required To Be Well Capitalized To Average Assets TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets	0.050
CY2019Q4	us-gaap	Common Equity Tier One Capital Required To Be Well Capitalized CommonEquityTierOneCapitalRequiredToBeWellCapitalized	0.065	USD
CY2019Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.080
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.060
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.040
CY2019Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	0.045	USD
CY2018Q4	us-gaap	Capital Required To Be Well Capitalized To Risk Weighted Assets CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.100
CY2018Q4	us-gaap	Tier One Risk Based Capital Required To Be Well Capitalized To Risk Weighted Assets TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets	0.080
CY2018Q4	us-gaap	Tier One Leverage Capital Required To Be Well Capitalized To Average Assets TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets	0.050
CY2018Q4	us-gaap	Common Equity Tier One Capital Required To Be Well Capitalized CommonEquityTierOneCapitalRequiredToBeWellCapitalized	0.065	USD
CY2018Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.080
CY2018Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.060
CY2018Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.040
CY2018Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	0.045	USD
CY2019	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Amount DefinedContributionPlanMaximumAnnualContributionsPerEmployeeAmount	19000	USD
CY2019	wal	Defined Contribution Plan Age Of Participants DefinedContributionPlanAgeOfParticipants	P50Y
CY2019	wal	Defined Contribution Plan Age Of Participants DefinedContributionPlanAgeOfParticipants	P50Y
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CY2018	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	5600000	USD
CY2017	us-gaap	Defined Contribution Plan Employer Discretionary Contribution Amount DefinedContributionPlanEmployerDiscretionaryContributionAmount	3100000	USD
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	569000	USD
CY2018	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	512000	USD
CY2019	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-834000	USD
CY2018	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	-41000	USD
CY2019	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	270000	USD
CY2018	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	67000	USD
CY2018Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	9991000	USD
CY2017Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	8891000	USD
CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	632000	USD
CY2018	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	614000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	11756000	USD
CY2018Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	9991000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	11756000	USD
CY2018Q4	us-gaap	Defined Benefit Plan Accumulated Benefit Obligation DefinedBenefitPlanAccumulatedBenefitObligation	9991000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Discount Rate DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate	0.0525
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CY2019	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	632000	USD
CY2018	us-gaap	Defined Benefit Plan Service Cost DefinedBenefitPlanServiceCost	614000	USD
CY2019	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	569000	USD
CY2018	us-gaap	Defined Benefit Plan Interest Cost DefinedBenefitPlanInterestCost	512000	USD
CY2019	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	64000	USD
CY2018	us-gaap	Defined Benefit Plan Amortization Of Prior Service Cost Credit DefinedBenefitPlanAmortizationOfPriorServiceCostCredit	103000	USD
CY2019	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	159000	USD
CY2018	us-gaap	Defined Benefit Plan Amortization Of Gains Losses DefinedBenefitPlanAmortizationOfGainsLosses	164000	USD
CY2019	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1106000	USD
CY2018	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1065000	USD
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CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Adjustment Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent	-61000	USD
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CY2018	wal	Loansand Leases Receivable Advances Related Parties LoansandLeasesReceivableAdvancesRelatedParties	0	USD
CY2019	us-gaap	Repayment Of Notes Receivable From Related Parties RepaymentOfNotesReceivableFromRelatedParties	1091000	USD
CY2018	us-gaap	Repayment Of Notes Receivable From Related Parties RepaymentOfNotesReceivableFromRelatedParties	1338000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	3812000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	4580000	USD
CY2019	us-gaap	Interest Income Related Party InterestIncomeRelatedParty	200000	USD
CY2018	us-gaap	Interest Income Related Party InterestIncomeRelatedParty	300000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	4580000	USD
CY2017Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	5918000	USD
CY2019	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	0	USD
CY2017	us-gaap	Interest Income Related Party InterestIncomeRelatedParty	500000	USD
CY2019Q4	wal	Loanand Leases Receivable Commitment Outstanding Related Parties LoanandLeasesReceivableCommitmentOutstandingRelatedParties	10600000	USD
CY2018Q4	wal	Loanand Leases Receivable Commitment Outstanding Related Parties LoanandLeasesReceivableCommitmentOutstandingRelatedParties	30700000	USD
CY2019Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	100100000	USD
CY2018Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	87900000	USD
CY2019	us-gaap	Interest Expense Related Party InterestExpenseRelatedParty	300000	USD
CY2018	us-gaap	Interest Expense Related Party InterestExpenseRelatedParty	200000	USD
CY2019	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	1000000.0	USD
CY2018	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	8100000	USD
CY2018	us-gaap	Related Party Transaction Expenses From Transactions With Related Party RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty	8100000	USD
CY2018Q4	wal	Related Party Oreo Sale RelatedPartyOREOSale	900000	USD
CY2018	wal	Related Party Losson Oreo Sale RelatedPartyLossonOREOSale	200000	USD
CY2019Q4	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	4471200000	USD
CY2019Q4	wal	Loansand Leases Receivable Including Heldfor Sale Net LoansandLeasesReceivableIncludingHeldforSaleNet	20955500000	USD
CY2019Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	13900000	USD
CY2019Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	297600000	USD
CY2019Q4	wal	Other Assets Segment OtherAssetsSegment	1083700000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	65095000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	482781000	USD
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CY2019Q4	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	393600000	USD
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CY2019Q4	us-gaap	Liabilities Liabilities	23805200000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3016700000	USD
CY2019Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	26821900000	USD
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CY2018Q4	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	4259700000	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
CY2018Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	299200000	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
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CY2018Q4	us-gaap	Liabilities Liabilities	20495800000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2613700000	USD
CY2018Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	23109500000	USD
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CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	1040412000	USD
CY2019	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	18500000	USD
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CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	105055000	USD
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CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	915879000	USD
CY2018	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	23000000	USD
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CY2018	us-gaap	Noninterest Income NoninterestIncome	43116000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	425667000	USD
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CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	74540000	USD
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CY2017	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	17250000	USD
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CY2017	us-gaap	Noninterest Income NoninterestIncome	45344000	USD
CY2017	us-gaap	Noninterest Expense NoninterestExpense	360941000	USD
CY2019	wal	Success Fees SuccessFees	1580000	USD
CY2019	wal	Othernoninterestincome Othernoninterestincome	288000	USD
CY2019	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	31060000	USD
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CY2017	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	126325000	USD
CY2017	us-gaap	Net Income Loss NetIncomeLoss	325492000	USD
CY2019	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	23353000	USD
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CY2019	us-gaap	Noninterest Income NoninterestIncome	65095000	USD
CY2018	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	22295000	USD
CY2018	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	6801000	USD
CY2018	wal	Success Fees SuccessFees	3335000	USD
CY2018	wal	Othernoninterestincome Othernoninterestincome	626000	USD
CY2018	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	33057000	USD
CY2018	wal	Otherrevenue Otherrevenue	10059000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	43116000	USD
CY2019Q4	us-gaap	Billed Contract Receivables BilledContractReceivables	1600000	USD
CY2018Q4	us-gaap	Billed Contract Receivables BilledContractReceivables	1400000	USD
CY2019Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	315420000	USD
CY2019Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	315608000	USD
CY2019Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	302848000	USD
CY2019Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	291168000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	43447000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	49186000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	48167000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	43832000	USD
CY2019Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	271973000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	266422000	USD
CY2019Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	254681000	USD
CY2019Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	247336000	USD
CY2019Q4	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	4000000	USD
CY2019Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	4000000	USD
CY2019Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	7000000	USD
CY2019Q1	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	3500000	USD
CY2019Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	267973000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	262422000	USD
CY2019Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	247681000	USD
CY2019Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	243836000	USD
CY2019Q2	us-gaap	Noninterest Income NoninterestIncome	14218000	USD
CY2019Q1	us-gaap	Noninterest Income NoninterestIncome	15410000	USD
CY2019Q4	us-gaap	Noninterest Expense NoninterestExpense	129699000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	125955000	USD
CY2019Q4	us-gaap	Noninterest Income NoninterestIncome	16027000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
CY2019Q2	us-gaap	Noninterest Expense NoninterestExpense	114213000	USD
CY2019Q1	us-gaap	Noninterest Expense NoninterestExpense	112914000	USD
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.16
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	154301000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	155908000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	147686000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	146332000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	26236000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28533000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	24750000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	25536000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	128065000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	122936000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	120796000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.26
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.19
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.16
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.25
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.19
CY2018Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	281968000	USD
CY2018Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	265216000	USD
CY2018Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	251602000	USD
CY2018Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	234697000	USD
CY2018Q4	us-gaap	Interest Expense InterestExpense	38455000	USD
CY2018Q3	us-gaap	Interest Expense InterestExpense	31178000	USD
CY2018Q2	us-gaap	Interest Expense InterestExpense	27494000	USD
CY2018Q1	us-gaap	Interest Expense InterestExpense	20477000	USD
CY2018Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	243513000	USD
CY2018Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	234038000	USD
CY2018Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	224108000	USD
CY2018Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	214220000	USD
CY2018Q4	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6000000	USD
CY2018Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6000000	USD
CY2018Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	5000000	USD
CY2018Q1	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6000000	USD
CY2018Q4	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	237513000	USD
CY2018Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	228038000	USD
CY2018Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	219108000	USD
CY2018Q1	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	208220000	USD
CY2018Q3	us-gaap	Noninterest Income NoninterestIncome	4418000	USD
CY2018Q2	us-gaap	Noninterest Income NoninterestIncome	13444000	USD
CY2018Q2	us-gaap	Noninterest Expense NoninterestExpense	102548000	USD
CY2018Q4	us-gaap	Noninterest Income NoninterestIncome	13611000	USD
CY2018Q1	us-gaap	Noninterest Income NoninterestIncome	11643000	USD
CY2018Q4	us-gaap	Noninterest Expense NoninterestExpense	111129000	USD
CY2018Q3	us-gaap	Noninterest Expense NoninterestExpense	113841000	USD
CY2018Q1	us-gaap	Noninterest Expense NoninterestExpense	98149000	USD
CY2018Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	139995000	USD
CY2018Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	118615000	USD
CY2018Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	130004000	USD
CY2018Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	121714000	USD
CY2018Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	20909000	USD
CY2018Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	7492000	USD
CY2018Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	25325000	USD
CY2018Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	20814000	USD
CY2018Q4	us-gaap	Net Income Loss NetIncomeLoss	119086000	USD
CY2018Q3	us-gaap	Net Income Loss NetIncomeLoss	111123000	USD
CY2018Q2	us-gaap	Net Income Loss NetIncomeLoss	104679000	USD
CY2018Q1	us-gaap	Net Income Loss NetIncomeLoss	100900000	USD
CY2018Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.14
CY2018Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.06
CY2018Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.00
CY2018Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.97
CY2018Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.13
CY2018Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.05
CY2018Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.99
CY2018Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.96

Files In Submission

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$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

2019 Q4 Form 10-K Financial Statement

#000121254520000104 Filed on March 02, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL WESTERN ALLIANCE BANCORPORATION Stock $wal

2019 Q4 Form 10-K Financial Statement

#000121254520000104 Filed on March 02, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal