$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

$wal Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-Q Financial Statement

#000121254520000170 Filed on October 30, 2020

Income Statement

Concept	2020 Q4	2020 Q3	2019 Q4
Revenue	$331.6M	$304.8M	$315.4M
YoY Change	5.14%	-3.42%	11.86%
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	$5.800M	$7.600M	$5.000M
YoY Change	16.0%	61.7%	31.58%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$16.80M	$20.10M	$43.40M
YoY Change	-61.29%	-59.15%	12.86%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$240.6M	$166.6M	$154.3M
YoY Change	55.93%	6.93%	10.22%
Income Tax	$47.00M	$30.80M	$26.20M
% Of Pretax Income	19.53%	18.49%	16.98%
Net Earnings	$193.6M	$135.8M	$128.1M
YoY Change	51.13%	6.68%	7.57%
Net Earnings / Revenue	58.38%	44.55%	40.62%
Basic Earnings Per Share	$1.94	$1.36	$1.26
Diluted Earnings Per Share	$1.93	$1.36	$1.25
COMMON SHARES
Basic Shares Outstanding	100.8M shares	99.90M shares	102.6M shares
Diluted Shares Outstanding		100.1M shares

Balance Sheet

Concept	2020 Q4	2020 Q3	2019 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$2.672B	$1.419B	$434.6M
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	$134.1M	$128.3M	$125.8M
YoY Change	6.6%	2.55%	5.29%
Goodwill	$289.9M		$289.9M
YoY Change	0.0%		0.0%
Intangibles			$7.713M
YoY Change			-16.71%
Long-Term Investments	$167.0M	$161.0M	$139.0M
YoY Change	20.14%	26.77%	20.87%
Other Assets	$31.00M	$47.00M	$18.00M
YoY Change	72.22%	1075.0%	-43.75%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$36.46B	$33.34B	$26.82B
YoY Change	35.94%	26.63%	16.06%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses	$80.00M	$79.00M	$78.00M
YoY Change	2.56%	-1.25%
Deferred Revenue
YoY Change
Short-Term Debt	$21.00M	$10.00M	$0.00
YoY Change			-100.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$80.00M	$79.00M	$78.00M
YoY Change	2.56%	-1.25%	254.55%
LONG-TERM LIABILITIES
Long-Term Debt	$549.0M	$629.0M	$394.0M
YoY Change	39.34%	61.7%	9.44%
Other Long-Term Liabilities	$467.0M	$541.0M	$520.0M
YoY Change	-10.19%	13.42%	17.12%
Total Long-Term Liabilities	$1.016B	$1.170B	$914.0M
YoY Change	11.16%	35.1%	13.68%
TOTAL LIABILITIES
Total Short-Term Liabilities	$80.00M	$79.00M	$78.00M
Total Long-Term Liabilities	$1.016B	$1.170B	$914.0M
Total Liabilities	$33.05B	$30.11B	$23.81B
YoY Change	38.82%	28.68%	16.15%
SHAREHOLDERS EQUITY
Retained Earnings	$2.001B	$1.833B	$1.680B
YoY Change	19.11%	15.87%	31.0%
Common Stock	$1.391B	$10.00K	$10.00K
YoY Change	13908900.0%	0.0%	0.0%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$71.10M	$71.10M	$62.70M
YoY Change	13.4%	13.46%	18.12%
Treasury Stock Shares	2.169M shares	2.168M shares	2.004M shares
Shareholders Equity	$3.414B	$3.224B	$3.017B
YoY Change
Total Liabilities & Shareholders Equity	$36.46B	$33.34B	$26.82B
YoY Change	35.94%	26.63%	16.06%

Cashflow Statement

Concept	2020 Q4	2020 Q3	2019 Q4
OPERATING ACTIVITIES
Net Income	$193.6M	$135.8M	$128.1M
YoY Change	51.13%	6.68%	7.57%
Depreciation, Depletion And Amortization	$5.800M	$7.600M	$5.000M
YoY Change	16.0%	61.7%	31.58%
Cash From Operating Activities	$220.1M	$166.7M	$183.3M
YoY Change	20.08%	-18.36%	26.68%
INVESTING ACTIVITIES
Capital Expenditures	$6.300M	-$13.40M	-$19.80M
YoY Change	-131.82%	119.67%	560.0%
Acquisitions
YoY Change
Other Investing Activities	-$1.952B	-$1.520B	-$928.0M
YoY Change	110.33%	14.75%	-13.13%
Cash From Investing Activities	-$1.946B	-$1.534B	-$947.8M
YoY Change	105.28%	15.23%	-11.52%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	2.978B	1.267B	327.1M
YoY Change	810.55%	36.09%	-54.86%
NET CHANGE
Cash From Operating Activities	220.1M	166.7M	183.3M
Cash From Investing Activities	-1.946B	-1.534B	-947.8M
Cash From Financing Activities	2.978B	1.267B	327.1M
Net Change In Cash	1.253B	-99.70M	-437.4M
YoY Change	-386.44%	-49.03%	116.64%
FREE CASH FLOW
Cash From Operating Activities	$220.1M	$166.7M	$183.3M
Capital Expenditures	$6.300M	-$13.40M	-$19.80M
Free Cash Flow	$213.8M	$180.1M	$203.1M
YoY Change	5.27%	-14.36%	37.51%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Entity Central Index Key EntityCentralIndexKey	0001212545
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	dei	Amendment Flag AmendmentFlag	false
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	us-gaap	Lease Cost LeaseCost	9500000	USD
	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	3000000.0	USD
	dei	Document Type DocumentType	10-Q
	dei	Document Quarterly Report DocumentQuarterlyReport	true
	dei	Document Period End Date DocumentPeriodEndDate	2020-09-30
	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
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	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
	dei	Entity Small Business EntitySmallBusiness	false
	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
	dei	Entity Shell Company EntityShellCompany	false
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	wal	Lendingrelatedfees Lendingrelatedfees	2072000	USD
	wal	Lendingrelatedfees Lendingrelatedfees	1343000	USD
CY2020Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	0	USD
CY2019Q3	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	230000	USD
	us-gaap	Realized Gain Loss On Marketable Securities Cost Method Investments And Other Investments RealizedGainLossOnMarketableSecuritiesCostMethodInvestmentsAndOtherInvestments	3152000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	5882000	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	222000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-986000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4628000	USD
CY2020Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1947000	USD
CY2019Q3	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1869000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	3972000	USD
	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	4509000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	20606000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
	us-gaap	Noninterest Income NoninterestIncome	46985000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2019Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.75
CY2020Q3	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	3246000	USD
CY2020Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	78757000	USD
CY2019Q3	us-gaap	Labor And Related Expense LaborAndRelatedExpense	70978000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	220455000	USD
	us-gaap	Labor And Related Expense LaborAndRelatedExpense	205328000	USD
CY2020Q3	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	10034000	USD
CY2019Q3	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	8248000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	31105000	USD
	wal	Legal Professional And Director Fees LegalProfessionalAndDirectorFees	26885000	USD
CY2020Q3	us-gaap	Occupancy Net OccupancyNet	9426000	USD
CY2019Q3	us-gaap	Occupancy Net OccupancyNet	8263000	USD
	us-gaap	Occupancy Net OccupancyNet	25752000	USD
	us-gaap	Occupancy Net OccupancyNet	24251000	USD
CY2020Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	8864000	USD
CY2019Q3	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	7095000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	26044000	USD
	us-gaap	Information Technology And Data Processing InformationTechnologyAndDataProcessing	20563000	USD
CY2019Q3	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	11537000	USD
	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	14098000	USD
	wal	Non Interest Expense Deposit Costs NonInterestExpenseDepositCosts	24930000	USD
CY2020Q3	us-gaap	General Insurance Expense GeneralInsuranceExpense	3064000	USD
CY2019Q3	us-gaap	General Insurance Expense GeneralInsuranceExpense	3071000	USD
	us-gaap	General Insurance Expense GeneralInsuranceExpense	9506000	USD
	us-gaap	General Insurance Expense GeneralInsuranceExpense	8691000	USD
CY2020Q3	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	1771000	USD
CY2019Q3	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	1953000	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	5280000	USD
	wal	Loan And Repossessed Asset Expense LoanAndRepossessedAssetExpense	5419000	USD
CY2020Q3	us-gaap	Business Development BusinessDevelopment	950000	USD
CY2019Q3	us-gaap	Business Development BusinessDevelopment	1443000	USD
	us-gaap	Business Development BusinessDevelopment	4062000	USD
	us-gaap	Business Development BusinessDevelopment	4972000	USD
CY2020Q3	us-gaap	Marketing Expense MarketingExpense	848000	USD
CY2019Q3	us-gaap	Marketing Expense MarketingExpense	842000	USD
	us-gaap	Marketing Expense MarketingExpense	2621000	USD
	us-gaap	Marketing Expense MarketingExpense	2640000	USD
CY2020Q3	wal	Cardexpense Cardexpense	505000	USD
CY2019Q3	wal	Cardexpense Cardexpense	548000	USD
	wal	Cardexpense Cardexpense	1631000	USD
	wal	Cardexpense Cardexpense	1892000	USD
CY2020Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	373000	USD
CY2019Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	387000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1120000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1161000	USD
CY2020Q3	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	123000	USD
CY2019Q3	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	3379000	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	-1335000	USD
	wal	Net Loss Gain On Sales Valuations Of Repossessed Assets And Bank Premises Net NetLossGainOnSalesValuationsOfRepossessedAssetsAndBankPremisesNet	2856000	USD
CY2020Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6131000	USD
CY2019Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8408000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	19033000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	22691000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	124092000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	126152000	USD
	us-gaap	Noninterest Expense NoninterestExpense	359372000	USD
	us-gaap	Noninterest Expense NoninterestExpense	352279000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	166591000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	155908000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	381934000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	449926000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	30822000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28533000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	68929000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	78819000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	135769000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
	us-gaap	Net Income Loss NetIncomeLoss	313005000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.36
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.12
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.36
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.11
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.59
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	99850000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102041000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	100322000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	103024000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100059000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	102451000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100574000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103468000	shares
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	135769000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
	us-gaap	Net Income Loss NetIncomeLoss	313005000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	2520000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	3592000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	17310000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	25523000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	7592000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	11014000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	53176000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	78314000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	1000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	6000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	94000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax	18000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	3000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	18000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	296000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	53000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	874000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	196000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	285000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodTax	2173000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	2681000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	598000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	871000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	6664000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	776000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	56000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	776000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	174000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4908000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	53577000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	140677000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	136593000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	366582000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	440328000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	2851264000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	19000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	6060000	USD
CY2019Q3	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	1531000	USD
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	43658000	USD
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	25684000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2923063000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	3102414000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	135769000	USD
CY2020Q3	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	73000	USD
CY2020Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	6605000	USD
CY2020Q3	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	515000	USD
CY2020Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	25208000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4908000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	3224046000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2613734000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	55000	USD
	us-gaap	Net Income Loss NetIncomeLoss	313005000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	19783000	USD
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	9582000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	115571000	USD
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	25684000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2923063000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	3016748000	USD
CY2020Q1	us-gaap	Stockholders Equity StockholdersEquity	2991801000	USD
	us-gaap	Net Income Loss NetIncomeLoss	313005000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	170000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	21560000	USD
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	8370000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	71669000	USD
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	76028000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	53577000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	3224046000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	157837000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	15303000	USD
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	17122000	USD
	us-gaap	Depreciation And Amortization DepreciationAndAmortization	14904000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	21560000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	19783000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	-37414000	USD
	us-gaap	Deferred Income Taxes And Tax Credits DeferredIncomeTaxesAndTaxCredits	5757000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-19015000	USD
	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-11031000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	34244000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	33551000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	8874000	USD
	us-gaap	Operating Lease Expense OperatingLeaseExpense	7704000	USD
	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	34085000	USD
	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	31838000	USD
	us-gaap	Life Insurance Corporate Or Bank Owned Change In Value LifeInsuranceCorporateOrBankOwnedChangeInValue	3370000	USD
	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2938000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	230000	USD
	us-gaap	Debt And Equity Securities Realized Gain Loss DebtAndEquitySecuritiesRealizedGainLoss	3152000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	-986000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	4628000	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	0	USD
	us-gaap	Gain Loss On Sales Of Loans Net GainLossOnSalesOfLoansNet	-530000	USD
	wal	Bank Owned Life Insurance Enhancement BankOwnedLifeInsuranceEnhancement	5607000	USD
	wal	Bank Owned Life Insurance Enhancement BankOwnedLifeInsuranceEnhancement	0	USD
	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	1335000	USD
	wal	Gain Loss On Foreclosed Assets GainLossOnForeclosedAssets	-2856000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	40486000	USD
	us-gaap	Increase Decrease In Other Operating Capital Net IncreaseDecreaseInOtherOperatingCapitalNet	-94535000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	450116000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	534505000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	1720604000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	746445000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	1014380000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	453307000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	156629000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities ProceedsFromSaleOfAvailableForSaleSecurities	150377000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	106772000	USD
	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	100460000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	16894000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	18206000	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	0	USD
	us-gaap	Proceeds From Sale Of Held To Maturity Securities ProceedsFromSaleOfHeldToMaturitySecurities	10000000	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	31075000	USD
	wal	Paymentsto Acquire Securities Equity PaymentstoAcquireSecuritiesEquity	10662000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	7003000	USD
	us-gaap	Proceeds From Dividends Received ProceedsFromDividendsReceived	4535000	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	103365000	USD
	wal	Purchase Of Investment Tax Credits PurchaseOfInvestmentTaxCredits	88074000	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	-1463000	USD
	wal	Purchaseof Sbic Investments PurchaseofSBICInvestments	5298000	USD
	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	0	USD
	wal	Proceedsfrom Sale Paymentsto Purchase Investment In Money Market ProceedsfromSalePaymentstoPurchaseInvestmentInMoneyMarket	7000	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	6011000	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	334000	USD
	us-gaap	Payments To Acquire Restricted Investments PaymentsToAcquireRestrictedInvestments	244000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	4806138000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	2445769000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	33103000	USD
	us-gaap	Payments For Proceeds From Productive Assets PaymentsForProceedsFromProductiveAssets	15282000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	7073000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	628000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-5591938000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-2775174000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	6046903000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	3263367000	USD
	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	221942000	USD
	us-gaap	Proceeds From Issuance Of Subordinated Long Term Debt ProceedsFromIssuanceOfSubordinatedLongTermDebt	0	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	13013000	USD
	us-gaap	Proceeds From Repayments Of Debt ProceedsFromRepaymentsOfDebt	-498429000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	170000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	55000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	8370000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	9582000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	71669000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	115571000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	76028000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	25684000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	6125961000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2614156000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	984139000	USD
	us-gaap	Cash And Cash Equivalents Period Increase Decrease CashAndCashEquivalentsPeriodIncreaseDecrease	373487000	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
CY2020Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	1418735000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	872059000	USD
	us-gaap	Interest Paid InterestPaid	87134000	USD
	us-gaap	Interest Paid InterestPaid	144680000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	37069000	USD
	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	-26228000	USD
	wal	Number Of Wholly Owned Subsidiaries Non Bank Subsidiaries NumberOfWhollyOwnedSubsidiariesNonBankSubsidiaries	2	Subsidiary
CY2019Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	167797000	USD
CY2019Q4	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	18025000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	8955000	USD
CY2019Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	1680317000	USD
	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: the determination of the allowance for credit losses; certain assets and liabilities carried at fair value; and 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>
CY2020Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	504477000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	43663000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2020Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	548140000	USD
CY2020Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3876586000	USD
CY2020Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	116671000	USD
CY2020Q3	us-gaap	Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	18032000	USD
CY2020Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3975225000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Cost EquitySecuritiesFvNiCost	158164000	USD
CY2020Q3	wal	Equitysecurities Fvni Accumulated Gross Unrealized Gain Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedGainBeforeTax	4331000	USD
CY2020Q3	wal	Equitysecurities Fvni Accumulated Gross Unrealized Loss Before Tax EquitysecuritiesFVNIAccumulatedGrossUnrealizedLossBeforeTax	1934000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	160561000	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	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	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
CY2020Q3	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	830400000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Other Debt Securities Available For Sale Or Held For Investment PledgedFinancialInstrumentsNotSeparatelyReportedOtherDebtSecuritiesAvailableForSaleOrHeldForInvestment	962500000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	3028000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	427743000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	15004000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	120636000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	18032000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	548379000	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
CY2020Q3	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	73	positions
CY2019Q4	us-gaap	Availableforsale Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions1 AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1	158	positions
CY2020Q2	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	7649000	USD
CY2020Q3	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	-1685000	USD
CY2020Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Writeoff DebtSecuritiesHeldToMaturityAllowanceForCreditLossWriteoff	0	USD
CY2020Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Recovery DebtSecuritiesHeldToMaturityAllowanceForCreditLossRecovery	0	USD
CY2020Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	5964000	USD
CY2020Q1	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	2646000	USD
	us-gaap	Debt Securities Held To Maturity Credit Loss Expense Reversal DebtSecuritiesHeldToMaturityCreditLossExpenseReversal	3318000	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
CY2020Q3	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	5964000	USD
CY2020Q3	us-gaap	Accrued Investment Income Receivable AccruedInvestmentIncomeReceivable	1800000	USD
CY2020Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3975225000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	160561000	USD
CY2019Q4	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3346310000	USD
CY2019Q4	us-gaap	Equity Securities Fv Ni EquitySecuritiesFvNi	138701000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	7330000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	7336000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	17135000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	17628000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	480012000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	523176000	USD
CY2020Q3	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	504477000	USD
CY2020Q3	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	548140000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	600000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	600000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	9024000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	9047000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	229899000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	223844000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	970304000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	1020284000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost	2666759000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue	2721450000	USD
CY2020Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3876586000	USD
CY2020Q3	us-gaap	Available For Sale Securities AvailableForSaleSecurities	3975225000	USD
CY2020Q3	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	0	USD
CY2019Q3	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3152000	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	405000	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3152000	USD
CY2020Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
CY2019Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	175000	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	0	USD
CY2019Q3	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	3152000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	230000	USD
	us-gaap	Debt Securities Available For Sale Realized Gain Loss DebtSecuritiesAvailableForSaleRealizedGainLoss	3152000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	25993254000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	310560000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	25682694000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	167797000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	20933696000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	81400000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	47700000	USD
CY2020Q3	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	22100000	USD
CY2019Q4	us-gaap	Receivable With Imputed Interest Premium ReceivableWithImputedInterestPremium	19600000	USD
CY2020Q3	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	20800000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Amount LoansReceivableHeldForSaleAmount	21800000	USD
CY2020Q3	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	108239000	USD
CY2020Q3	wal	Financing Receivable Nonaccrual With Allowance FinancingReceivableNonaccrualWithAllowance	17470000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	125709000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	28129000	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
CY2020Q3	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	1700000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	700000	USD
	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	4100000	USD
	us-gaap	Loans And Leases Receivable Impaired Interest Lost On Nonaccrual Loans LoansAndLeasesReceivableImpairedInterestLostOnNonaccrualLoans	1500000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	25940867000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	52387000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	25993254000	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	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	21101493000	USD
CY2020Q3	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	4966577000	USD
CY2020Q3	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	5479907000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	3191331000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	1829321000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	728405000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	1999527000	USD
CY2020Q3	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	7798186000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	25993254000	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
CY2020Q3	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	60800000	USD
CY2020Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	20	SecurityLoan
CY2020Q3	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	25000000.0	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	22	SecurityLoan
	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	35700000	USD
CY2020Q3	wal	Reserves Allocated To Customers Whose Loan Terms Modified In Troubled Debt Restructurings ReservesAllocatedToCustomersWhoseLoanTermsModifiedInTroubledDebtRestructurings	2700000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	4200000	USD
CY2020Q3	wal	Financing Receivable Troubled Debt Restructured Loans Number Of Outstanding Contracts FinancingReceivableTroubledDebtRestructuredLoansNumberOfOutstandingContracts	27	SecurityLoan
CY2020Q3	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	60757000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	3	SecurityLoan
CY2019Q3	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	11800000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	7	SecurityLoan
	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	40700000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Impaired Commitment To Lend LoansAndLeasesReceivableImpairedCommitmentToLend	200000	USD
CY2020Q3	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	SecurityLoan
CY2020Q3	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	800000	USD
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	2	SecurityLoan
	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	1500000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	SecurityLoan
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	2	SecurityLoan
	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	400000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Collateral For Secured Borrowings LoansAndLeasesReceivableCollateralForSecuredBorrowings	254780000	USD
CY2020Q3	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	44400000	USD
CY2019Q4	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	9000000.0	USD
CY2020Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	310550000	USD
CY2020Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	8204000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	8773000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	579000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	310560000	USD
CY2020Q1	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	186925000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	134130000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	14593000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	4098000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	310560000	USD
CY2020Q3	us-gaap	Interest Receivable InterestReceivable	120100000	USD
CY2019Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	160409000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	2099000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	2711000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4000000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	165021000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	152717000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	6968000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	4772000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	14500000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	165021000	USD
CY2020Q3	us-gaap	Financing Receivable Collectively Evaluated For Impairment FinancingReceivableCollectivelyEvaluatedForImpairment	25654269000	USD
CY2020Q3	us-gaap	Financing Receivable Individually Evaluated For Impairment FinancingReceivableIndividuallyEvaluatedForImpairment	338985000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	25993254000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment	300514000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1	10046000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	310560000	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
CY2020Q3	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	514396000	USD
	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	1683720000	USD
	us-gaap	Financing Receivable Purchased With Credit Deterioration Amount At Purchase Price FinancingReceivablePurchasedWithCreditDeteriorationAmountAtPurchasePrice	0	USD
CY2020Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.25
	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.25
CY2019Q3	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	709071000	USD
CY2019Q3	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	14238000	USD
	us-gaap	Financing Receivable Significant Purchases FinancingReceivableSignificantPurchases	1830177000	USD
	us-gaap	Financing Receivable Significant Sales FinancingReceivableSignificantSales	49068000	USD
CY2019Q3	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	100000	USD
	us-gaap	Loans And Leases Receivable Gain Loss On Sales Net LoansAndLeasesReceivableGainLossOnSalesNet	-500000	USD
CY2020Q3	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2019Q4	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2020Q3	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	10000000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	0	USD
CY2020Q3	us-gaap	Short Term Borrowings ShortTermBorrowings	10000000	USD
CY2019Q4	us-gaap	Short Term Borrowings ShortTermBorrowings	0	USD
CY2020Q3	us-gaap	Federal Funds Purchased FederalFundsPurchased	0	USD
CY2020Q3	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	14398	shares
CY2020Q3	us-gaap	Federal Home Loan Bank Advances Maturities Summary Due Within One Year Of Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryDueWithinOneYearOfBalanceSheetDate	10000000.0	USD
CY2020Q3	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	19700000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase SecuritiesSoldUnderAgreementsToRepurchase	16700000	USD
CY2020Q3	us-gaap	Subordinated Debt SubordinatedDebt	545300000	USD
CY2019Q4	us-gaap	Subordinated Debt SubordinatedDebt	319200000	USD
	wal	Numberof Statutory Business Trusts Formedor Acquired NumberofStatutoryBusinessTrustsFormedorAcquired	8	Trust
CY2020Q3	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	73500000	USD
CY2019Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	74400000	USD
	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod	136334	shares
CY2020Q3	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	250000000.0	USD
	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	2066479	shares
	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	34.65
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	71700000	USD
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	1000000	shares
	us-gaap	Stock Repurchased And Retired During Period Shares StockRepurchasedAndRetiredDuringPeriodShares	2733603	shares
CY2019Q3	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	43.63
	wal	Weighted Average Selling Price Per Share WeightedAverageSellingPricePerShare	42.25
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	43700000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	115600000	USD
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	164564	shares
CY2020Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	35.73
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	50.86
CY2019Q3	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	33031	shares
	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	209183	shares
CY2019Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	46.33
	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	45.78
CY2020Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	73677000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	4908000	USD
CY2020Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	4908000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	78585000	USD
CY2019Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	26381000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	11594000	USD
CY2019Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	2376000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	9218000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	35599000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	25008000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	53751000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	174000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	53577000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	78585000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	33622000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	71597000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	2376000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	69221000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	35599000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	3152000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	230000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	3152000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	776000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	56000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	776000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	0	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	174000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	2376000	USD
CY2020Q3	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	596505000	USD
CY2020Q3	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	92352000	USD
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
CY2020Q3	us-gaap	Hedged Liability Fair Value Hedge HedgedLiabilityFairValueHedge	323386000	USD
CY2020Q3	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-3417000	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
CY2020Q3	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	14600000	USD
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	29200000	USD
CY2019Q3	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	31000000.0	USD
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	99850000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	102041000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	100322000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	103024000	shares
CY2020Q3	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	209000	shares
CY2019Q3	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	410000	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	252000	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	444000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100059000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	102451000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	100574000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	103468000	shares
CY2020Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	135769000	USD
CY2019Q3	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	127375000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	313005000	USD
	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	371107000	USD
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.36
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.25
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.12
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.60
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.36
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.11
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.59
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	900000	USD
CY2020Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1850
CY2019Q3	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1830
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1805
	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.1752
CY2020Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	46600000	USD
	us-gaap	Increase Decrease In Deferred Income Taxes IncreaseDecreaseInDeferredIncomeTaxes	28600000	USD
CY2020Q3	us-gaap	Deferred Income Tax Assets Net DeferredIncomeTaxAssetsNet	46600000	USD
CY2020Q3	us-gaap	Operating Loss Carryforwards Valuation Allowance OperatingLossCarryforwardsValuationAllowance	0	USD
CY2020Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	414300000	USD
CY2019Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	409400000	USD
CY2020Q3	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	161500000	USD
CY2019Q4	us-gaap	Investment Related Liabilities InvestmentRelatedLiabilities	191000000.0	USD
CY2020Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	14500000	USD
CY2019Q3	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	13000000.0	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	34200000	USD
	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	33600000	USD
	us-gaap	Line Of Credit Facility Expiration Period LineOfCreditFacilityExpirationPeriod	P1Y
	us-gaap	Noninterest Income NoninterestIncome	46985000	USD
CY2020Q3	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8819069000	USD
CY2019Q4	us-gaap	Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability FairValueDisclosureOffbalanceSheetRisksFaceAmountLiability	8827108000	USD
	wal	Maximum Loan To Value Ratio MaximumLoanToValueRatio	0.75
CY2020Q3	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.29
CY2019Q4	wal	Percentage Of Commercial Real Estate Loans Occupied By Owners PercentageOfCommercialRealEstateLoansOccupiedByOwners	0.31
CY2020Q3	us-gaap	Lease Cost LeaseCost	3900000	USD
	us-gaap	Lease Cost LeaseCost	10900000	USD
CY2019Q3	us-gaap	Lease Cost LeaseCost	3200000	USD
	us-gaap	Lease Cost LeaseCost	9500000	USD
CY2020Q3	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	1000000.0	USD
	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	2900000	USD
CY2019Q3	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	1000000.0	USD
	wal	Lesseeoperatingleaseothercost Lesseeoperatingleaseothercost	3000000.0	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	2681000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	598000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	871000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	6664000	USD
CY2020Q3	us-gaap	Fair Value Liabilities Measured On Recurring Basis Subordinated Debt Obligations FairValueLiabilitiesMeasuredOnRecurringBasisSubordinatedDebtObligations	60529000	USD
CY2020Q3	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	92352000	USD
CY2020Q3	us-gaap	Hedged Liability Fair Value Hedge Cumulative Increase Decrease HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease	-3417000	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
CY2020Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	2700000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	600000	USD
	us-gaap	Other Comprehensive Income Loss Financial Liability Fair Value Option Unrealized Gain Loss Arising During Period After Tax OtherComprehensiveIncomeLossFinancialLiabilityFairValueOptionUnrealizedGainLossArisingDuringPeriodAfterTax	6700000	USD
CY2020Q3	wal	Collateral Dependent Loans Allowance CollateralDependentLoansAllowance	-9600000	USD
CY2020Q3	wal	Cash Cash Equivalentsand Investment Securities CashCashEquivalentsandInvestmentSecurities	6119800000	USD
CY2020Q3	wal	Loansand Leases Receivable Including Heldfor Sale Net LoansandLeasesReceivableIncludingHeldforSaleNet	25703500000	USD
CY2020Q3	us-gaap	Other Foreclosed Assets OtherForeclosedAssets	8600000	USD
CY2020Q3	us-gaap	Intangible Assets Net Including Goodwill IntangibleAssetsNetIncludingGoodwill	299000000.0	USD
CY2020Q3	wal	Other Assets Segment OtherAssetsSegment	1204600000	USD
CY2020Q3	us-gaap	Assets Assets	33335500000	USD
CY2020Q3	us-gaap	Deposits Deposits	28843400000	USD
CY2020Q3	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	628800000	USD
CY2020Q3	wal	Other Liabilities Segment OtherLiabilitiesSegment	639300000	USD
CY2020Q3	us-gaap	Liabilities Liabilities	30111500000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	3224000000.0	USD
CY2020Q3	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	33335500000	USD
CY2020Q3	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2020Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	284738000	USD
CY2020Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	14661000	USD
CY2020Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	270077000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	20606000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	124092000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	166591000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	30822000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	135769000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	852158000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	157837000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	694321000	USD
	us-gaap	Noninterest Expense NoninterestExpense	359372000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	381934000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	68929000	USD
	us-gaap	Net Income Loss NetIncomeLoss	313005000	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
CY2019Q4	us-gaap	Assets Assets	26821900000	USD
CY2019Q4	us-gaap	Deposits Deposits	22796500000	USD
CY2019Q4	wal	Borrowingsand Qualifying Debt BorrowingsandQualifyingDebt	393600000	USD
CY2019Q4	wal	Other Liabilities Segment OtherLiabilitiesSegment	615100000	USD
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
CY2019Q4	wal	Excess Funds Providedby Usedin Segment Basis ExcessFundsProvidedbyUsedinSegmentBasis	0	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	266422000	USD
CY2019Q3	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	3803000	USD
CY2019Q3	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	262619000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	126152000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	155908000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	28533000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	127375000	USD
	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	768439000	USD
	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	15303000	USD
	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	753136000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
	us-gaap	Noninterest Expense NoninterestExpense	352279000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	449926000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	78819000	USD
	us-gaap	Net Income Loss NetIncomeLoss	371107000	USD
CY2020Q3	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5913000	USD
CY2020Q3	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	1597000	USD
CY2020Q3	wal	Success Fees SuccessFees	38000	USD
CY2020Q3	wal	Othernoninterestincome Othernoninterestincome	69000	USD
CY2020Q3	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	7617000	USD
CY2020Q3	wal	Otherrevenue Otherrevenue	12989000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	20606000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	17447000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	3942000	USD
	wal	Success Fees SuccessFees	423000	USD
	wal	Othernoninterestincome Othernoninterestincome	231000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	22043000	USD
	wal	Otherrevenue Otherrevenue	24942000	USD
	us-gaap	Noninterest Income NoninterestIncome	46985000	USD
CY2019Q3	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	5888000	USD
CY2019Q3	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	1977000	USD
CY2019Q3	wal	Success Fees SuccessFees	605000	USD
CY2019Q3	wal	Othernoninterestincome Othernoninterestincome	80000	USD
CY2019Q3	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	8550000	USD
CY2019Q3	wal	Otherrevenue Otherrevenue	10891000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	19441000	USD
	us-gaap	Fees And Commissions Mortgage Banking And Servicing FeesAndCommissionsMortgageBankingAndServicing	17121000	USD
	wal	Debitandcreditcardinterchangefees Debitandcreditcardinterchangefees	5830000	USD
	wal	Success Fees SuccessFees	1125000	USD
	wal	Othernoninterestincome Othernoninterestincome	187000	USD
	us-gaap	Contract With Customer Liability Revenue Recognized ContractWithCustomerLiabilityRevenueRecognized	24263000	USD
	wal	Otherrevenue Otherrevenue	24806000	USD
	us-gaap	Noninterest Income NoninterestIncome	49069000	USD
CY2020Q3	us-gaap	Accounts Receivable Net AccountsReceivableNet	1500000	USD
CY2019Q4	us-gaap	Accounts Receivable Net AccountsReceivableNet	1600000	USD

Files In Submission

Name	View Source	Status
0001212545-20-000170-index-headers.html	Edgar Link	pending
0001212545-20-000170-index.html	Edgar Link	pending
0001212545-20-000170.txt	Edgar Link	pending
0001212545-20-000170-xbrl.zip	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
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report.css	Edgar Link	pending
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wal-20200930.htm	Edgar Link	pending
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wal-20200930_cal.xml	Edgar Link	unprocessable
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wal-20200930_htm.xml	Edgar Link	completed
wal-20200930_lab.xml	Edgar Link	unprocessable
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walex3119302020.htm	Edgar Link	pending
walex3129302020.htm	Edgar Link	pending
walex329302020.htm	Edgar Link	pending

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$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal

2020 Q4 Form 10-Q Financial Statement

#000121254520000170 Filed on October 30, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL WESTERN ALLIANCE BANCORPORATION Stock $wal

2020 Q4 Form 10-Q Financial Statement

#000121254520000170 Filed on October 30, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$WAL
WESTERN ALLIANCE BANCORPORATION Stock $wal