$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

$wal Overview Financials Valuation SEC Filings Company Website

2021 Q2 Form 10-Q Financial Statement

#000121254521000151 Filed on July 30, 2021

Income Statement

Concept	2021 Q2	2020 Q2
Revenue	$398.5M	$318.2M
YoY Change	25.24%	5.05%
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	$9.000M	$4.500M
YoY Change	100.0%	-2.17%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$28.00M	$19.80M
YoY Change	41.41%	-58.92%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$276.2M	$112.9M
YoY Change	144.64%	-23.61%
Income Tax	$52.40M	$19.60M
% Of Pretax Income	18.97%	17.36%
Net Earnings	$223.8M	$93.30M
YoY Change	139.87%	-24.15%
Net Earnings / Revenue	56.16%	29.32%
Basic Earnings Per Share	$2.18	$0.93
Diluted Earnings Per Share	$2.17	$0.93
COMMON SHARES
Basic Shares Outstanding	102.7M shares	99.80M shares
Diluted Shares Outstanding	103.4M shares	100.0M shares

Balance Sheet

Concept	2021 Q2	2020 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$3.396B	$1.519B
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	$150.2M	$127.8M
YoY Change	17.51%	3.85%
Goodwill	$199.8M
YoY Change
Intangibles
YoY Change
Long-Term Investments	$194.0M	$138.0M
YoY Change	40.58%	20.0%
Other Assets	$37.00M	$34.00M
YoY Change	8.82%	277.78%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$49.07B	$31.91B
YoY Change	53.79%	26.04%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$102.0M	$77.00M
YoY Change	32.47%	1.32%
Deferred Revenue
YoY Change
Short-Term Debt	$57.60M	$10.00M
YoY Change	476.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$102.0M	$77.00M
YoY Change	32.47%	1.32%
LONG-TERM LIABILITIES
Long-Term Debt	$1.698B	$618.0M
YoY Change	174.76%	59.69%
Other Long-Term Liabilities	$1.256B	$529.0M
YoY Change	137.43%	-3.11%
Total Long-Term Liabilities	$2.954B	$1.147B
YoY Change	157.54%	22.94%
TOTAL LIABILITIES
Total Short-Term Liabilities	$102.0M	$77.00M
Total Long-Term Liabilities	$2.954B	$1.147B
Total Liabilities	$45.03B	$28.80B
YoY Change	56.35%	28.23%
SHAREHOLDERS EQUITY
Retained Earnings	$2.367B	$1.722B
YoY Change	37.4%	13.77%
Common Stock	$1.688B	$10.00K
YoY Change	16875900.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$84.20M	$70.58M
YoY Change	19.29%	15.46%
Treasury Stock Shares	2.326M shares
Shareholders Equity	$4.035B	$3.102B
YoY Change
Total Liabilities & Shareholders Equity	$49.07B	$31.91B
YoY Change	53.79%	26.04%

Cashflow Statement

Concept	2021 Q2	2020 Q2
OPERATING ACTIVITIES
Net Income	$223.8M	$93.30M
YoY Change	139.87%	-24.15%
Depreciation, Depletion And Amortization	$9.000M	$4.500M
YoY Change	100.0%	-2.17%
Cash From Operating Activities	-$2.061B	$159.4M
YoY Change	-1393.16%	-10.95%
INVESTING ACTIVITIES
Capital Expenditures	-$3.200M	-$3.100M
YoY Change	3.23%	-48.33%
Acquisitions
YoY Change
Other Investing Activities	-$1.322B	-$1.659B
YoY Change	-20.34%	52.68%
Cash From Investing Activities	-$1.325B	-$1.662B
YoY Change	-20.3%	52.14%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	1.436B	2.606B
YoY Change	-44.91%	117.9%
NET CHANGE
Cash From Operating Activities	-2.061B	159.4M
Cash From Investing Activities	-1.325B	-1.662B
Cash From Financing Activities	1.436B	2.606B
Net Change In Cash	-1.951B	1.103B
YoY Change	-276.9%	290.89%
FREE CASH FLOW
Cash From Operating Activities	-$2.061B	$159.4M
Capital Expenditures	-$3.200M	-$3.100M
Free Cash Flow	-$2.058B	$162.5M
YoY Change	-1366.52%	-12.16%

Facts In Submission

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	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2021
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q2
	dei	Amendment Flag AmendmentFlag	false
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
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	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2021-06-30
	dei	Document Transition Report DocumentTransitionReport	false
	dei	Entity File Number EntityFileNumber	001-32550
	dei	Entity Registrant Name EntityRegistrantName	WESTERN ALLIANCE BANCORPORATION
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	DE
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	88-0365922
	dei	Entity Address Address Line1 EntityAddressAddressLine1	One E. Washington Street, Suite 1400
	dei	Entity Address City Or Town EntityAddressCityOrTown	Phoenix
	dei	Entity Address State Or Province EntityAddressStateOrProvince	AZ
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	85004
	dei	City Area Code CityAreaCode	602
	dei	Local Phone Number LocalPhoneNumber	389-3500
	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
	dei	Entity Filer Category EntityFilerCategory	Large Accelerated Filer
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CY2021Q2	wal	Loan Servicing Fees Net LoanServicingFeesNet	-20800000	USD
CY2020Q2	wal	Loan Servicing Fees Net LoanServicingFeesNet	0	USD
	wal	Loan Servicing Fees Net LoanServicingFeesNet	-20800000	USD
	wal	Loan Servicing Fees Net LoanServicingFeesNet	0	USD
CY2021Q2	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	500000	USD
CY2020Q2	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	200000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	800000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	300000	USD
CY2021Q2	us-gaap	Noninterest Income NoninterestIncome	136000000.0	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	21300000	USD
	us-gaap	Noninterest Income NoninterestIncome	155700000	USD
	us-gaap	Noninterest Income NoninterestIncome	26400000	USD
CY2021Q2	us-gaap	Expense Related To Distribution Or Servicing And Underwriting Fees ExpenseRelatedToDistributionOrServicingAndUnderwritingFees	22300000	USD
CY2021Q2	us-gaap	Labor And Related Expense LaborAndRelatedExpense	128900000	USD
CY2020Q2	us-gaap	Labor And Related Expense LaborAndRelatedExpense	69600000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	212600000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	141700000	USD
CY2020Q2	us-gaap	Expense Related To Distribution Or Servicing And Underwriting Fees ExpenseRelatedToDistributionOrServicingAndUnderwritingFees	0	USD
	us-gaap	Expense Related To Distribution Or Servicing And Underwriting Fees ExpenseRelatedToDistributionOrServicingAndUnderwritingFees	22300000	USD
	us-gaap	Expense Related To Distribution Or Servicing And Underwriting Fees ExpenseRelatedToDistributionOrServicingAndUnderwritingFees	0	USD
CY2021Q2	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	15000000.0	USD
CY2020Q2	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	8600000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	24900000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	17200000	USD
CY2021Q2	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	14000000.0	USD
CY2020Q2	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	10700000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	24100000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	21100000	USD
CY2021Q2	us-gaap	Loan Processing Fee LoanProcessingFee	10500000	USD
CY2020Q2	us-gaap	Loan Processing Fee LoanProcessingFee	0	USD
	us-gaap	Loan Processing Fee LoanProcessingFee	10500000	USD
	us-gaap	Loan Processing Fee LoanProcessingFee	0	USD
CY2021Q2	us-gaap	Occupancy Net OccupancyNet	10400000	USD
CY2020Q2	us-gaap	Occupancy Net OccupancyNet	8100000	USD
	us-gaap	Occupancy Net OccupancyNet	19000000.0	USD
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CY2021Q2	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	7100000	USD
CY2020Q2	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	3500000	USD
	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	13400000	USD
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CY2021Q2	us-gaap	General Insurance Expense GeneralInsuranceExpense	5500000	USD
CY2020Q2	us-gaap	General Insurance Expense GeneralInsuranceExpense	3400000	USD
	us-gaap	General Insurance Expense GeneralInsuranceExpense	9700000	USD
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CY2021Q2	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	2500000	USD
CY2020Q2	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	2000000.0	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	4700000	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	3500000	USD
CY2021Q2	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1800000	USD
CY2020Q2	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	400000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	2300000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	800000	USD
CY2021Q2	us-gaap	Marketing Expense MarketingExpense	1700000	USD
CY2020Q2	us-gaap	Marketing Expense MarketingExpense	900000	USD
	us-gaap	Marketing Expense MarketingExpense	2300000	USD
	us-gaap	Marketing Expense MarketingExpense	1800000	USD
CY2021Q2	us-gaap	Business Development BusinessDevelopment	1500000	USD
CY2020Q2	us-gaap	Business Development BusinessDevelopment	800000	USD
	us-gaap	Business Development BusinessDevelopment	2300000	USD
	us-gaap	Business Development BusinessDevelopment	3100000	USD
CY2021Q2	wal	Cardexpense Cardexpense	600000	USD
CY2020Q2	wal	Cardexpense Cardexpense	400000	USD
	wal	Cardexpense Cardexpense	1200000	USD
	wal	Cardexpense Cardexpense	1100000	USD
CY2021Q2	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-1500000	USD
CY2020Q2	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	0.0	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-1800000	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-1400000	USD
CY2021Q2	wal	Acquisition And Restructure Expenses AcquisitionAndRestructureExpenses	15700000	USD
CY2020Q2	wal	Acquisition And Restructure Expenses AcquisitionAndRestructureExpenses	0	USD
	wal	Acquisition And Restructure Expenses AcquisitionAndRestructureExpenses	16100000	USD
	wal	Acquisition And Restructure Expenses AcquisitionAndRestructureExpenses	0	USD
CY2021Q2	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8800000	USD
CY2020Q2	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6400000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	16200000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	12900000	USD
CY2021Q2	us-gaap	Noninterest Expense NoninterestExpense	244800000	USD
CY2020Q2	us-gaap	Noninterest Expense NoninterestExpense	114800000	USD
	us-gaap	Noninterest Expense NoninterestExpense	379800000	USD
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CY2021Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	276200000	USD
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	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	215300000	USD
CY2021Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	52400000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19600000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	94300000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38100000	USD
CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	223800000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	93300000	USD
	us-gaap	Net Income Loss NetIncomeLoss	416300000	USD
	us-gaap	Net Income Loss NetIncomeLoss	177200000	USD
CY2021Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.18
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.93
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CY2021Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.93
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CY2021Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102700000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	99800000	shares
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CY2021Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103400000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100000000.0	shares
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	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100800000	shares
CY2021Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2020Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
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CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	223800000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	93300000	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	14600000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	12800000	USD
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	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	14800000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	44800000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	39300000	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0.0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	0.0	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-0.0	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	0.0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	-1000000.0	USD
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CY2020Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3000000.0	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-0.0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0.0	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	100000	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	44600000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	36200000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-27800000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	48700000	USD
CY2021Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	268400000	USD
CY2020Q2	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	129500000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	388500000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	225900000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	2999600000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	93300000	USD
CY2020Q2	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	8100000	USD
CY2020Q2	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	400000	USD
CY2020Q2	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	9200000	USD
CY2020Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	25200000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	36200000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	3102400000	USD
CY2021Q1	us-gaap	Stockholders Equity StockholdersEquity	3712700000	USD
CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	223800000	USD
CY2021Q2	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	9600000	USD
CY2021Q2	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	200000	USD
CY2021Q2	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	69800000	USD
CY2021Q2	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	25800000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	44600000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	4034500000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3016700000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	2991800000	USD
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	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	15100000	USD
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	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	50800000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	48700000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	3102400000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	3413500000	USD
	us-gaap	Net Income Loss NetIncomeLoss	416300000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	17700000	USD
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	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	279000000.0	USD
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	51100000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-27800000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	4034500000	USD
	us-gaap	Net Income Loss NetIncomeLoss	416300000	USD
	us-gaap	Net Income Loss NetIncomeLoss	177200000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	23700000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	19700000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	6700000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	46900000	USD
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	us-gaap	Depreciation And Amortization DepreciationAndAmortization	15000000.0	USD
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	us-gaap	Share Based Compensation ShareBasedCompensation	17500000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	15000000.0	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	10300000	USD
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	us-gaap	Operating Lease Expense OperatingLeaseExpense	2800000	USD
	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	38700000	USD
	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	23700000	USD
	us-gaap	Life Insurance Corporate Or Bank Owned Change In Value LifeInsuranceCorporateOrBankOwnedChangeInValue	1900000	USD
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	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	22678800000	USD
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	0	USD
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	us-gaap	Servicing Asset At Fair Value Additions ServicingAssetAtFairValueAdditions	282300000	USD
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	us-gaap	Increase Decrease In Loans Held For Sale IncreaseDecreaseInLoansHeldForSale	13200000	USD
	us-gaap	Increase Decrease In Loans Held For Sale IncreaseDecreaseInLoansHeldForSale	0	USD
	us-gaap	Servicing Asset At Fair Value Period Increase Decrease ServicingAssetAtFairValuePeriodIncreaseDecrease	-60900000	USD
	us-gaap	Servicing Asset At Fair Value Period Increase Decrease ServicingAssetAtFairValuePeriodIncreaseDecrease	0	USD
	us-gaap	Increase Decrease In Derivative Assets And Liabilities IncreaseDecreaseInDerivativeAssetsAndLiabilities	27400000	USD
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	wal	Gain Loss On Sale And Valuation Of Investment Securities And Other Assets Net GainLossOnSaleAndValuationOfInvestmentSecuritiesAndOtherAssetsNet	-3400000	USD
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	wal	Bank Owned Life Insurance Enhancement BankOwnedLifeInsuranceEnhancement	0	USD
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	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	2927200000	USD
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	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	963300000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	618900000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	0	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	156600000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	406400000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	49200000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	4400000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	8300000	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	28400000	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	7900000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	2400000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	4100000	USD
	wal	Proceedsfrom Saleof Equitysecurities Fvni ProceedsfromSaleofEquitysecuritiesFVNI	600000	USD
	wal	Proceedsfrom Saleof Equitysecurities Fvni ProceedsfromSaleofEquitysecuritiesFVNI	0	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	47700000	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	62500000	USD
	us-gaap	Proceeds From Sale Of Mortgage Servicing Rights Msr ProceedsFromSaleOfMortgageServicingRightsMSR	-777600000	USD
	us-gaap	Proceeds From Sale Of Mortgage Servicing Rights Msr ProceedsFromSaleOfMortgageServicingRightsMSR	0	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	9400000	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	-3000000.0	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	5600000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	2686100000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	3826100000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	13600000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	13300000	USD
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	1013400000	USD
	us-gaap	Payments To Acquire Businesses Net Of Cash Acquired PaymentsToAcquireBusinessesNetOfCashAcquired	0	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-5383900000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-4058200000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	9990500000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	4748100000	USD
	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	592300000	USD
	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	222100000	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-2728600000	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	18800000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	12900000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	7800000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	71700000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	51100000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	50800000	USD
	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	279000000.0	USD
	us-gaap	Proceeds From Issuance Of Common Stock ProceedsFromIssuanceOfCommonStock	0	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	8069200000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	4858700000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	724100000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	1083900000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	2671700000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	434600000	USD
CY2021Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	3395800000	USD
CY2020Q2	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1518500000	USD
	us-gaap	Interest Paid InterestPaid	94400000	USD
	us-gaap	Interest Paid InterestPaid	61500000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	111100000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	16400000	USD
	wal	Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries NumberOfWhollyOwnedSubsidiariesNonBankSubsidiaries	2	Subsidiary
	us-gaap	Use Of Estimates UseOfEstimates	Use of estimatesThe 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 susceptible to significant changes in the near term, particularly to the extent that economic conditions worsen or persist longer than expected in an adverse state, relate to: 1) the determination of the allowance for credit losses; 2) certain assets and liabilities carried at fair value; and 3) accounting for income taxes.
	wal	Number Of Unconsolidated Subsidiaries NumberOfUnconsolidatedSubsidiaries	8	Subsidiary
	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="margin-top:9pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Reclassifications</span></div><div style="margin-top:9pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">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>
	us-gaap	Business Combination Acquisition Related Costs BusinessCombinationAcquisitionRelatedCosts	3400000	USD
CY2021Q2	us-gaap	Business Acquisition Effective Date Of Acquisition1 BusinessAcquisitionEffectiveDateOfAcquisition1	2021-04-07
	wal	Payments To Acquire Business Premium Amount PaymentsToAcquireBusinessPremiumAmount	275000000.0	USD
	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	1200000000	USD
	wal	Acquisition And Restructure Expenses AcquisitionAndRestructureExpenses	16100000	USD
CY2021Q2	us-gaap	Business Acquisition Effective Date Of Acquisition1 BusinessAcquisitionEffectiveDateOfAcquisition1	2021-04-07
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Cash And Equivalents BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents	207200000	USD
CY2021Q2	wal	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Loans Held For Sale BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansHeldForSale	3553700000	USD
CY2021Q2	wal	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Servicing Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedServicingAssets	1376300000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Property Plant And Equipment BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment	11300000	USD
CY2021Q2	wal	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Operating Right Of Use Asset BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingRightOfUseAsset	19000000.0	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles	139500000	USD
CY2021Q2	wal	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Loans Eligible For Repurchase BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoansEligibleForRepurchase	2744700000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deferred Tax Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets	6500000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Other Noncurrent Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets	240600000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Assets BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets	8298800000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Long Term Debt BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt	3633900000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Capital Lease Obligation BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCapitalLeaseObligation	19000000.0	USD
CY2021Q2	wal	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Liability For Loans Eligible For Repurchase BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilityForLoansEligibleForRepurchase	2744700000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Noncurrent Liabilities Other BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther	157400000	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Liabilities BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities	6555000000.0	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet	1743800000	USD
	us-gaap	Payments To Acquire Businesses Gross PaymentsToAcquireBusinessesGross	1220600000	USD
CY2021Q2	wal	Business Combination Elimination Of Pre Existing Debt And Other BusinessCombinationEliminationOfPreExistingDebtAndOther	698200000	USD
	us-gaap	Business Combination Consideration Transferred1 BusinessCombinationConsiderationTransferred1	1918800000	USD
CY2021Q2	us-gaap	Goodwill Goodwill	175000000.0	USD
CY2021Q2	us-gaap	Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles	139500000	USD
CY2021Q2	us-gaap	Goodwill Goodwill	175000000.0	USD
CY2021Q2	us-gaap	Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount	150000000.0	USD
CY2021Q2	wal	Business Acquisition Pro Forma Interest Income BusinessAcquisitionProFormaInterestIncome	400500000	USD
CY2020Q2	wal	Business Acquisition Pro Forma Interest Income BusinessAcquisitionProFormaInterestIncome	331400000	USD
	wal	Business Acquisition Pro Forma Interest Income BusinessAcquisitionProFormaInterestIncome	753800000	USD
	wal	Business Acquisition Pro Forma Interest Income BusinessAcquisitionProFormaInterestIncome	661900000	USD
CY2021Q2	wal	Business Acquisition Pro Forma Non Interest Income BusinessAcquisitionProFormaNonInterestIncome	132400000	USD
CY2020Q2	wal	Business Acquisition Pro Forma Non Interest Income BusinessAcquisitionProFormaNonInterestIncome	304800000	USD
	wal	Business Acquisition Pro Forma Non Interest Income BusinessAcquisitionProFormaNonInterestIncome	222000000.0	USD
	wal	Business Acquisition Pro Forma Non Interest Income BusinessAcquisitionProFormaNonInterestIncome	425100000	USD
CY2021Q2	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	243800000	USD
CY2020Q2	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	253100000	USD
	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	424000000.0	USD
	us-gaap	Business Acquisitions Pro Forma Net Income Loss BusinessAcquisitionsProFormaNetIncomeLoss	389000000.0	USD
CY2021Q2	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	968700000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	46100000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	2100000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	1012700000	USD
CY2021Q2	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	6529200000	USD
CY2021Q2	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	139800000	USD
CY2021Q2	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	53800000	USD
CY2021Q2	us-gaap	Available For Sale Securities AvailableForSaleSecurities	6615200000	USD
CY2021Q2	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	185000000.0	USD
CY2021Q2	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	9000000.0	USD
CY2021Q2	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	200000	USD
CY2021Q2	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	193800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	568800000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	43000000.0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	611800000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	4586400000	USD
CY2020Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	137600000	USD
CY2020Q4	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	15500000	USD
CY2020Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	4708500000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	160100000	USD
CY2020Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	7600000	USD
CY2020Q4	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	400000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	167300000	USD
CY2021Q2	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	2400000000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	778000000.0	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	49400000	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	2246300000	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	4500000	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	35100000	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	53900000	USD
CY2021Q2	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	2281400000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	4400000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	398900000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	11100000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	120800000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	15500000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	519700000	USD
CY2021Q2	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	130	positions
CY2020Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	49	positions
CY2021Q1	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	9200000	USD
CY2021Q2	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	3200000	USD
CY2021Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
CY2021Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2021Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	6000000.0	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	6800000	USD
	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	-800000	USD
	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2021Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	6000000.0	USD
CY2020Q1	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	3000000.0	USD
CY2020Q2	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	4600000	USD
CY2020Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
CY2020Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2020Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7600000	USD
CY2019Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	2600000	USD
	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	5000000.0	USD
	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2020Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7600000	USD
CY2021Q2	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	2600000	USD
CY2020Q4	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	2000000.0	USD
CY2021Q2	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	968700000	USD
CY2021Q2	us-gaap	Available For Sale Securities AvailableForSaleSecurities	6615200000	USD
CY2021Q2	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	193800000	USD
CY2020Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	4708500000	USD
CY2020Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	167300000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	35800000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	35800000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	17700000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	18000000.0	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	685000000.0	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	728700000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateNetCarryingAmount	230200000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Debt Maturities Without Single Maturity Date Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	230200000	USD
CY2021Q2	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	968700000	USD
CY2021Q2	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	1012700000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	9300000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	9300000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	45300000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	46700000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	829900000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	831400000	USD
CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	1738300000	USD
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CY2021Q2	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	3897600000	USD
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CY2021Q2	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	79600000	USD
CY2020Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	78900000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	152418	shares
CY2021Q2	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	700000	shares
CY2021Q2	us-gaap	Shares Issued Price Per Share SharesIssuedPricePerShare	100.59
	us-gaap	Adjustments To Additional Paid In Capital Stock Issued Issuance Costs AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts	600000	USD
CY2021Q1	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	2300000	shares
CY2021Q1	us-gaap	Shares Issued Price Per Share SharesIssuedPricePerShare	91.00
	us-gaap	Proceeds From Issuance Of Private Placement ProceedsFromIssuanceOfPrivatePlacement	209200000	USD
CY2021Q2	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	250000000.0	USD
CY2020Q2	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	297000	shares
	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	2066479	shares
CY2020Q2	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	30.77
	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	34.65
CY2020Q2	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	9200000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	71700000	USD
CY2021Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.25
CY2020Q2	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.25
CY2021Q2	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	2256	shares
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	156419	shares
CY2021Q2	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	106.23
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	83.89
CY2020Q2	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	11055	shares
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	150166	shares
CY2020Q2	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	35.96
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	52.31
CY2021Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	19900000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	44600000	USD
CY2021Q2	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	0	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	44600000	USD
CY2021Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	64500000	USD
CY2020Q1	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	37500000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	36300000	USD
CY2020Q2	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	100000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	36200000	USD
CY2020Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	73700000	USD
CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	92300000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-27700000	USD
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	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-27800000	USD
CY2021Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	64500000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-25000000.0	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	48900000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	200000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	48700000	USD
CY2020Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	73700000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	100000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	100000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	200000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0.0	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-0.0	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	-0.0	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	0	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	100000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	100000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	200000	USD
CY2021Q2	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	1551600000	USD
CY2021Q2	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	57300000	USD
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	1587100000	USD
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	85500000	USD
CY2021Q2	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	244800000	USD
CY2021Q2	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-800000	USD
CY2020Q4	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	247600000	USD
CY2020Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-2700000	USD
CY2021Q2	us-gaap	Hedged Asset Fair Value Hedge Last Of Layer Amount HedgedAssetFairValueHedgeLastOfLayerAmount	1000000000.0	USD
CY2021Q2	us-gaap	Prepayable Financial Asset Closed Portfolio Last Of Layer Amortized Cost PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost	1500000000	USD
CY2020Q4	us-gaap	Prepayable Financial Asset Closed Portfolio Last Of Layer Amortized Cost PrepayableFinancialAssetClosedPortfolioLastOfLayerAmortizedCost	1900000000	USD
CY2021Q2	us-gaap	Hedged Asset Fair Value Hedge Last Of Layer Cumulative Increase Decrease HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease	8100000	USD
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge Last Of Layer Cumulative Increase Decrease HedgedAssetFairValueHedgeLastOfLayerCumulativeIncreaseDecrease	600000	USD
CY2021Q2	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	75700000	USD
CY2021Q2	wal	Derivative Netting Adjustments Assets DerivativeNettingAdjustmentsAssets	-31300000	USD
CY2021Q2	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	44400000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	4200000	USD
CY2020Q4	wal	Derivative Netting Adjustments Assets DerivativeNettingAdjustmentsAssets	-600000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	3600000	USD
CY2020Q2	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	6500000	USD
CY2020Q2	wal	Derivative Netting Adjustments Assets DerivativeNettingAdjustmentsAssets	0	USD
CY2020Q2	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	6500000	USD
CY2021Q2	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	103800000	USD
CY2021Q2	wal	Derivative Netting Adjustments Liabilities DerivativeNettingAdjustmentsLiabilities	31300000	USD
CY2021Q2	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	72500000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	87500000	USD
CY2020Q4	wal	Derivative Netting Adjustments Liabilities DerivativeNettingAdjustmentsLiabilities	600000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	86900000	USD
CY2020Q2	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	101800000	USD
CY2020Q2	wal	Derivative Netting Adjustments Liabilities DerivativeNettingAdjustmentsLiabilities	0	USD
CY2020Q2	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	101800000	USD
CY2021Q2	us-gaap	Derivative Liability Fair Value Of Collateral DerivativeLiabilityFairValueOfCollateral	103600000	USD
CY2020Q4	us-gaap	Derivative Liability Fair Value Of Collateral DerivativeLiabilityFairValueOfCollateral	117800000	USD
CY2020Q2	us-gaap	Derivative Liability Fair Value Of Collateral DerivativeLiabilityFairValueOfCollateral	117200000	USD
CY2021Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102700000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	99800000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	101800000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	100600000	shares
CY2021Q2	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	700000	shares
CY2020Q2	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	200000	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	600000	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	200000	shares
CY2021Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103400000	shares
CY2020Q2	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100000000.0	shares
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	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100800000	shares
CY2021Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	223800000	USD
CY2020Q2	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	93300000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	416300000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	177200000	USD
CY2021Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.18
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.93
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CY2021Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.93
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CY2021Q2	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.190
CY2020Q2	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.174
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CY2021Q2	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	36500000	USD
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CY2020Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	31300000	USD
CY2021Q2	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	36500000	USD
CY2021Q2	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2021Q2	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	490100000	USD
CY2020Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	405600000	USD
CY2021Q2	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	217800000	USD
CY2020Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	151700000	USD
CY2021Q2	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	8200000	USD
CY2020Q2	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	12300000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	23700000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	19700000	USD
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CY2021Q2	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	10995900000	USD
CY2020Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	9903600000	USD
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CY2021Q2	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.26
CY2020Q4	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.28
CY2021Q2	us-gaap	Lease Cost LeaseCost	4400000	USD
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CY2020Q2	us-gaap	Lease Cost LeaseCost	3500000	USD
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CY2021Q2	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	900000	USD
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CY2020Q2	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	900000	USD
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CY2021Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	200000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3000000.0	USD
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CY2021Q2	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	66500000	USD
CY2021Q2	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	57300000	USD
CY2021Q2	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-800000	USD
CY2020Q4	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	65900000	USD
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	85500000	USD
CY2020Q4	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-2700000	USD
CY2021Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	200000	USD
CY2020Q2	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	-3000000.0	USD
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CY2021Q2	wal	Fair Value Option Loans Held As Assets Current Through89 Days FairValueOptionLoansHeldAsAssetsCurrentThrough89Days	2251900000	USD
CY2021Q2	wal	Fair Value Option Loans Held As Assets Upb Current Through89 Days FairValueOptionLoansHeldAsAssetsUPBCurrentThrough89Days	2148700000	USD
CY2021Q2	wal	Fair Value Option Loans Held As Assets Current Through89 Days Aggregate Difference FairValueOptionLoansHeldAsAssetsCurrentThrough89DaysAggregateDifference	103200000	USD
CY2021Q2	us-gaap	Fair Value Option Loans Held As Assets90 Days Or More Past Due FairValueOptionLoansHeldAsAssets90DaysOrMorePastDue	700000	USD
CY2021Q2	wal	Fair Value Option Loans Held As Assets Upb90 Days Or More Past Due FairValueOptionLoansHeldAsAssetsUPB90DaysOrMorePastDue	800000	USD
CY2021Q2	us-gaap	Fair Value Option Loans Held As Assets90 Days Or More Past Due Aggregate Difference FairValueOptionLoansHeldAsAssets90DaysOrMorePastDueAggregateDifference	-100000	USD
CY2021Q2	wal	Fair Value Option Loans Held As Assets FairValueOptionLoansHeldAsAssets	2252600000	USD
CY2021Q2	us-gaap	Fair Value Option Loans Held As Assets Aggregate Difference FairValueOptionLoansHeldAsAssetsAggregateDifference	103100000	USD
CY2021Q2	wal	Collateral Dependent Loans Allowance CollateralDependentLoansAllowance	-13300000	USD
CY2021Q2	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	11240800000	USD
CY2021Q2	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	4465200000	USD
CY2021Q2	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	30026400000	USD
CY2021Q2	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	232900000	USD
CY2021Q2	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	29793500000	USD
CY2021Q2	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	3900000	USD
CY2021Q2	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	610700000	USD
CY2021Q2	wal	Other Assets Segment OtherAssetsSegment	2954900000	USD
CY2021Q2	us-gaap	Assets Assets	49069000000.0	USD
CY2021Q2	us-gaap	Deposits Deposits	41921000000.0	USD
CY2021Q2	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	1735200000	USD
CY2021Q2	wal	Other Liabilities Segment OtherLiabilitiesSegment	1378300000	USD
CY2021Q2	us-gaap	Liabilities Liabilities	45034500000	USD
CY2021Q2	us-gaap	Stockholders Equity StockholdersEquity	4034500000	USD
CY2021Q2	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	49069000000.0	USD
CY2021Q2	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2021Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	370500000	USD
CY2021Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	14500000	USD
CY2021Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	385000000.0	USD
CY2021Q2	us-gaap	Noninterest Income NoninterestIncome	136000000.0	USD
CY2021Q2	us-gaap	Noninterest Expense NoninterestExpense	244800000	USD
CY2021Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	276200000	USD
CY2021Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	52400000	USD
CY2021Q2	us-gaap	Net Income Loss NetIncomeLoss	223800000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	687800000	USD
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	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	94300000	USD
	us-gaap	Net Income Loss NetIncomeLoss	416300000	USD
CY2020Q4	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	8176500000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	27053000000.0	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	278900000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	26774100000	USD
CY2020Q4	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	1400000	USD
CY2020Q4	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	298500000	USD
CY2020Q4	wal	Other Assets Segment OtherAssetsSegment	1210500000	USD
CY2020Q4	us-gaap	Assets Assets	36461000000.0	USD
CY2020Q4	us-gaap	Deposits Deposits	31930500000	USD
CY2020Q4	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	553700000	USD
CY2020Q4	wal	Other Liabilities Segment OtherLiabilitiesSegment	563300000	USD
CY2020Q4	us-gaap	Liabilities Liabilities	33047500000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	3413500000	USD
CY2020Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	36461000000.0	USD
CY2020Q4	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2020Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	298400000	USD
CY2020Q2	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	92000000.0	USD
CY2020Q2	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	206400000	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	21300000	USD
CY2020Q2	us-gaap	Noninterest Expense NoninterestExpense	114800000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	112900000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	19600000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	93300000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	567400000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	143200000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	424200000	USD
	us-gaap	Noninterest Income NoninterestIncome	26400000	USD
	us-gaap	Noninterest Expense NoninterestExpense	235300000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	215300000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38100000	USD
	us-gaap	Net Income Loss NetIncomeLoss	177200000	USD
CY2021Q2	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	7400000	USD
CY2021Q2	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	1600000	USD
CY2021Q2	wal	Success Fees SuccessFees	0	USD
CY2021Q2	wal	Othernoninterestincome Othernoninterestincome	200000	USD
CY2021Q2	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	9200000	USD
CY2021Q2	wal	Otherrevenue Otherrevenue	126800000	USD
CY2021Q2	us-gaap	Noninterest Income NoninterestIncome	136000000.0	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	14100000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	2900000	USD
	wal	Success Fees SuccessFees	1000000.0	USD
	wal	Othernoninterestincome Othernoninterestincome	400000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	18400000	USD
	wal	Otherrevenue Otherrevenue	20800000	USD
	us-gaap	Noninterest Income NoninterestIncome	155700000	USD
CY2020Q2	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5100000	USD
CY2020Q2	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	900000	USD
CY2020Q2	wal	Success Fees SuccessFees	300000	USD
CY2020Q2	wal	Othernoninterestincome Othernoninterestincome	100000	USD
CY2020Q2	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	6400000	USD
CY2020Q2	wal	Otherrevenue Otherrevenue	14900000	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	21300000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	11500000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	2300000	USD
	wal	Success Fees SuccessFees	400000	USD
	wal	Othernoninterestincome Othernoninterestincome	200000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	14400000	USD
	wal	Otherrevenue Otherrevenue	12000000.0	USD
	us-gaap	Noninterest Income NoninterestIncome	26400000	USD
CY2021Q2	us-gaap	Accounts Receivable Net AccountsReceivableNet	2000000.0	USD
CY2020Q4	us-gaap	Accounts Receivable Net AccountsReceivableNet	1600000	USD

Files In Submission

Name	View Source	Status
0001212545-21-000151-index-headers.html	Edgar Link	pending
0001212545-21-000151-index.html	Edgar Link	pending
0001212545-21-000151.txt	Edgar Link	pending
0001212545-21-000151-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
image_0a.jpg	Edgar Link	pending
image_0b.jpg	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
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R9999.htm	Edgar Link	pending
report.css	Edgar Link	pending
Show.js	Edgar Link	pending
wal-20210630.htm	Edgar Link	pending
wal-20210630.xsd	Edgar Link	pending
wal-20210630_cal.xml	Edgar Link	unprocessable
wal-20210630_def.xml	Edgar Link	unprocessable
wal-20210630_htm.xml	Edgar Link	completed
wal-20210630_lab.xml	Edgar Link	unprocessable
wal-20210630_pre.xml	Edgar Link	unprocessable
walex102severanceandcicplan.htm	Edgar Link	pending
walex103epaceo.htm	Edgar Link	pending
walex104epanon-ceo.htm	Edgar Link	pending
walex3116302021.htm	Edgar Link	pending
walex3126302021.htm	Edgar Link	pending
walex326302021.htm	Edgar Link	pending

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$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

2021 Q2 Form 10-Q Financial Statement

#000121254521000151 Filed on July 30, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL WESTERN ALLIANCE BANCORPORATION Stock $wal

2021 Q2 Form 10-Q Financial Statement

#000121254521000151 Filed on July 30, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal