$COLB
Columbia Banking System Inc Stock $colb

$colb Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-Q Financial Statement

#000088734320000210 Filed on November 05, 2020

Income Statement

Concept	2020 Q4	2020 Q3	2019 Q3
Revenue	$133.3M	$127.4M	$132.5M
YoY Change	0.14%	-3.89%	3.89%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development		$7.095M	$5.102M
YoY Change		39.06%	14.24%
% of Gross Profit
Depreciation & Amortization	$400.0K	$4.100M	$8.900M
YoY Change	-95.0%	-53.93%	-1.11%
% of Gross Profit
Operating Expenses		$7.095M	$5.102M
YoY Change		39.06%	14.24%
Operating Profit
YoY Change
Interest Expense	$2.184M	$2.658M	$10.08M
YoY Change	-73.66%	-73.64%	110.99%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$75.07M	$54.68M	$63.11M
YoY Change	29.37%	-13.35%	9.14%
Income Tax	$16.77M	$9.949M	$12.38M
% Of Pretax Income	22.34%	18.19%	19.61%
Net Earnings	$58.30M	$44.73M	$50.73M
YoY Change	26.38%	-11.81%	9.29%
Net Earnings / Revenue	43.74%	35.12%	38.27%
Basic Earnings Per Share	$0.82	$0.63	$0.70
Diluted Earnings Per Share	$0.82	$0.63	$0.70
COMMON SHARES
Basic Shares Outstanding	71.61M shares	70.73M shares	71.80M shares
Diluted Shares Outstanding		70.76M shares	71.80M shares

Balance Sheet

Concept	2020 Q4	2020 Q3	2019 Q3
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$653.8M	$930.2M	$298.6M
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	$162.1M	$164.0M	$165.4M
YoY Change	-2.02%	-0.84%	-2.5%
Goodwill	$765.8M	$765.8M	$765.8M
YoY Change	0.0%	0.0%	0.0%
Intangibles	$26.73M	$28.75M	$37.91M
YoY Change	-24.6%	-24.17%	-22.36%
Long-Term Investments
YoY Change
Other Assets
YoY Change
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$16.58B	$16.23B	$13.76B
YoY Change	17.79%	17.99%	6.18%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses			$57.00M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$74.00M	$27.00M	$24.00M
YoY Change	15.63%	12.5%	-61.29%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$74.00M	$27.00M	$57.00M
YoY Change	17.46%	-52.63%	-8.06%
LONG-TERM LIABILITIES
Long-Term Debt	$35.00M	$35.00M	$35.00M
YoY Change	0.0%	0.0%	-2.78%
Other Long-Term Liabilities	$251.0M	$262.0M	$131.0M
YoY Change	110.92%	100.0%	22.43%
Total Long-Term Liabilities	$286.0M	$297.0M	$166.0M
YoY Change	85.71%	78.92%	16.08%
TOTAL LIABILITIES
Total Short-Term Liabilities	$74.00M	$27.00M	$57.00M
Total Long-Term Liabilities	$286.0M	$297.0M	$166.0M
Total Liabilities	$14.24B	$13.93B	$11.60B
YoY Change	19.44%	20.14%	5.66%
SHAREHOLDERS EQUITY
Retained Earnings	$575.2M	$537.0M	$493.7M
YoY Change	10.69%	8.76%	20.05%
Common Stock	$1.661B	$1.658B	$1.648B
YoY Change	0.62%	0.6%	0.5%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$70.83M	$70.83M	$45.38M
YoY Change	39.34%	56.09%
Treasury Stock Shares	2.184M shares	2.184M shares	1.300M shares
Shareholders Equity	$2.348B	$2.302B	$2.162B
YoY Change
Total Liabilities & Shareholders Equity	$16.58B	$16.23B	$13.76B
YoY Change	17.79%	17.99%	6.18%

Cashflow Statement

Concept	2020 Q4	2020 Q3	2019 Q3
OPERATING ACTIVITIES
Net Income	$58.30M	$44.73M	$50.73M
YoY Change	26.38%	-11.81%	9.29%
Depreciation, Depletion And Amortization	$400.0K	$4.100M	$8.900M
YoY Change	-95.0%	-53.93%	-1.11%
Cash From Operating Activities	$48.50M	$60.70M	$56.30M
YoY Change	-2.81%	7.82%	-0.71%
INVESTING ACTIVITIES
Capital Expenditures	-$1.200M	-$3.000M	-$2.300M
YoY Change	-53.85%	30.43%	-30.3%
Acquisitions
YoY Change
Other Investing Activities	-$620.4M	-$500.6M	-$586.9M
YoY Change	54.06%	-14.7%	63.03%
Cash From Investing Activities	-$621.6M	-$503.6M	-$589.2M
YoY Change	53.33%	-14.53%	62.22%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	296.6M	275.5M	572.8M
YoY Change	-2.59%	-51.9%	100.91%
NET CHANGE
Cash From Operating Activities	48.50M	60.70M	56.30M
Cash From Investing Activities	-621.6M	-503.6M	-589.2M
Cash From Financing Activities	296.6M	275.5M	572.8M
Net Change In Cash	-276.5M	-167.4M	39.90M
YoY Change	442.16%	-519.55%	-286.45%
FREE CASH FLOW
Cash From Operating Activities	$48.50M	$60.70M	$56.30M
Capital Expenditures	-$1.200M	-$3.000M	-$2.300M
Free Cash Flow	$49.70M	$63.70M	$58.60M
YoY Change	-5.33%	8.7%	-2.33%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
	dei	Entity Central Index Key EntityCentralIndexKey	0000887343
	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	Q3
	dei	Amendment Flag AmendmentFlag	false
	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	000-20288
	dei	Entity Address State Or Province EntityAddressStateOrProvince	WA
	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	98402-2156
	dei	Entity Registrant Name EntityRegistrantName	COLUMBIA BANKING SYSTEM, INC.
	dei	Entity Address City Or Town EntityAddressCityOrTown	Tacoma
	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	WA
	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	91-1422237
	dei	Entity Address Address Line1 EntityAddressAddressLine1	1301 A Street
	dei	City Area Code CityAreaCode	253
	dei	Local Phone Number LocalPhoneNumber	305-1900
	dei	Security12b Title Security12bTitle	Common Stock, No Par Value
	dei	Trading Symbol TradingSymbol	COLB
	dei	Security Exchange Name SecurityExchangeName	NASDAQ
	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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CY2020Q3	us-gaap	Occupancy Net OccupancyNet	8734000	USD
CY2019Q3	us-gaap	Occupancy Net OccupancyNet	8645000	USD
	us-gaap	Occupancy Net OccupancyNet	26743000	USD
	us-gaap	Occupancy Net OccupancyNet	26166000	USD
CY2020Q3	us-gaap	Communications And Information Technology CommunicationsAndInformationTechnology	4510000	USD
CY2019Q3	us-gaap	Communications And Information Technology CommunicationsAndInformationTechnology	5102000	USD
	us-gaap	Communications And Information Technology CommunicationsAndInformationTechnology	14804000	USD
	us-gaap	Communications And Information Technology CommunicationsAndInformationTechnology	14372000	USD
CY2020Q3	us-gaap	Professional Fees ProfessionalFees	3000000	USD
CY2019Q3	us-gaap	Professional Fees ProfessionalFees	5683000	USD
	us-gaap	Professional Fees ProfessionalFees	8585000	USD
	us-gaap	Professional Fees ProfessionalFees	16810000	USD
CY2020Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	2193000	USD
CY2019Q3	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	2632000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	6713000	USD
	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	8029000	USD
CY2020Q3	colb	Taxes Licenses And Fees TaxesLicensesAndFees	1559000	USD
CY2019Q3	colb	Taxes Licenses And Fees TaxesLicensesAndFees	1325000	USD
	colb	Taxes Licenses And Fees TaxesLicensesAndFees	3427000	USD
	colb	Taxes Licenses And Fees TaxesLicensesAndFees	4612000	USD
CY2020Q3	us-gaap	Advertising Expense AdvertisingExpense	680000	USD
CY2019Q3	us-gaap	Advertising Expense AdvertisingExpense	1752000	USD
	us-gaap	Advertising Expense AdvertisingExpense	2822000	USD
	us-gaap	Advertising Expense AdvertisingExpense	3596000	USD
CY2020Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	826000	USD
CY2019Q3	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	-38000	USD
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1894000	USD
	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1902000	USD
CY2020Q3	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-160000	USD
CY2019Q3	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-90000	USD
	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-348000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	85115000	USD
	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-682000	USD
CY2020Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8640000	USD
CY2019Q3	us-gaap	Other Noninterest Expense OtherNoninterestExpense	7606000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	29561000	USD
	us-gaap	Other Noninterest Expense OtherNoninterestExpense	25140000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	87076000	USD
	us-gaap	Noninterest Expense NoninterestExpense	250219000	USD
	us-gaap	Noninterest Expense NoninterestExpense	258504000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	54683000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	63105000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	117318000	USD
	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	183579000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	9949000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12378000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	21374000	USD
	us-gaap	Net Income Loss NetIncomeLoss	148322000	USD
	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	35257000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	44734000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	50727000	USD
	us-gaap	Net Income Loss NetIncomeLoss	95944000	USD
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.63
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.70
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.35
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.04
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.63
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.70
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.35
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.04
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70726000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	71803000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70870000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72256000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	70762000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72257000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	71803000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	70906000	shares
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	44734000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	50727000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	436000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-4421000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-1442000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	14593000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-1442000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	14593000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-24000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-19000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax	80000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax	62000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-80000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-62000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	19000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-951000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	-62000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	3137000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	621000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	18000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	2052000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	58000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-2114000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	3079000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-3476000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	17734000	USD
CY2020Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	41258000	USD
CY2019Q3	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	68461000	USD
	us-gaap	Net Income Loss NetIncomeLoss	95944000	USD
	us-gaap	Net Income Loss NetIncomeLoss	148322000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-36690000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-26209000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	121114000	USD
	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	86519000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	58000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	496000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	191000	USD
	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1636000	USD
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	120923000	USD
	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	84883000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-72000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-56000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax	239000	USD
	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax	184000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-239000	USD
	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-184000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-6218000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-4599000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	20526000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	15180000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	1349000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	18000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	4454000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	58000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	16072000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	15122000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	137234000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	100189000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	233178000	USD
	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	248511000	USD
CY2020Q2	us-gaap	Stockholders Equity StockholdersEquity	2276755000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	44734000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-3476000	USD
CY2020Q3	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	1083000	USD
CY2020Q3	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	-2000	USD
CY2020Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	3009000	USD
CY2020Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	16000	USD
CY2020Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.28
CY2020Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	20106000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	2301981000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	2159962000	USD
	us-gaap	Net Income Loss NetIncomeLoss	95944000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	137234000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	2028000	USD
	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	2000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	7918000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2498000	USD
	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.06
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	76152000	USD
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	20000000	USD
CY2020Q3	us-gaap	Stockholders Equity StockholdersEquity	2301981000	USD
CY2019Q2	us-gaap	Stockholders Equity StockholdersEquity	2133638000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	50727000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	17734000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	1132000	USD
CY2019Q3	colb	Stock Adjustment Deferred Compensation Shares StockAdjustmentDeferredCompensationShares	0	shares
CY2019Q3	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	1000	USD
CY2019Q3	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	1000	USD
CY2019Q3	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	2299000	USD
CY2019Q3	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	19000	USD
CY2019Q3	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.28
CY2019Q3	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	20418000	USD
CY2019Q3	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	23517000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2161577000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2033649000	USD
	us-gaap	Net Income Loss NetIncomeLoss	148322000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	100189000	USD
	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	2025000	USD
	colb	Stock Adjustment Deferred Compensation Shares StockAdjustmentDeferredCompensationShares	0	shares
	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	2000	USD
	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	2000	USD
	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	6827000	USD
	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2765000	USD
	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.12
	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	82074000	USD
	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	45380000	USD
CY2019Q3	us-gaap	Stockholders Equity StockholdersEquity	2161577000	USD
	us-gaap	Net Income Loss NetIncomeLoss	95944000	USD
	us-gaap	Net Income Loss NetIncomeLoss	148322000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	82400000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1879000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	7918000	USD
	us-gaap	Share Based Compensation ShareBasedCompensation	6827000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	14456000	USD
	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	26150000	USD
	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	16674000	USD
	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	2132000	USD
	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	953000	USD
	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	6787000	USD
	colb	Netgainlossonsaleandvaluationadjustmentsof Oreo NetgainlossonsaleandvaluationadjustmentsofOREO	64000	USD
	colb	Netgainlossonsaleandvaluationadjustmentsof Oreo NetgainlossonsaleandvaluationadjustmentsofOREO	602000	USD
	colb	Gainonbankownedlifeinsurancedeathbenefit Gainonbankownedlifeinsurancedeathbenefit	0	USD
	colb	Gainonbankownedlifeinsurancedeathbenefit Gainonbankownedlifeinsurancedeathbenefit	2975000	USD
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	356962000	USD
	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	134634000	USD
	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	350273000	USD
	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	123447000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	9879000	USD
	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	3180000	USD
	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-399000	USD
	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	632000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	53996000	USD
	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	31840000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	31703000	USD
	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	29706000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	143767000	USD
	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	154813000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	938624000	USD
	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	305581000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	996951000	USD
	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	649133000	USD
	us-gaap	Payments To Acquire Loans Receivable PaymentsToAcquireLoansReceivable	0	USD
	us-gaap	Payments To Acquire Loans Receivable PaymentsToAcquireLoansReceivable	57075000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	7538000	USD
	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	5833000	USD
	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	53240000	USD
	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	190800000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	194105000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	259554000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Equity ProceedsFromSaleOfAvailableForSaleSecuritiesEquity	3000000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Equity ProceedsFromSaleOfAvailableForSaleSecuritiesEquity	0	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	406767000	USD
	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	287479000	USD
	us-gaap	Proceeds From Sales Of Assets Investing Activities ProceedsFromSalesOfAssetsInvestingActivities	2128000	USD
	us-gaap	Proceeds From Sales Of Assets Investing Activities ProceedsFromSalesOfAssetsInvestingActivities	7735000	USD
	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	91080000	USD
	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	187080000	USD
	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	1034000	USD
	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	6433000	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1050000	USD
	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1297189000	USD
	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-460141000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	2915565000	USD
	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	397893000	USD
	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-37471000	USD
	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	-36605000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Advances ProceedsFromFederalHomeLoanBankAdvances	1331000000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Advances ProceedsFromFederalHomeLoanBankAdvances	4770000000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	222010000	USD
	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	36000000	USD
	us-gaap	Proceeds From Other Debt ProceedsFromOtherDebt	9222000	USD
	us-gaap	Proceeds From Other Debt ProceedsFromOtherDebt	100000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2028000	USD
	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2025000	USD
	us-gaap	Payments For Federal Home Loan Bank Advances PaymentsForFederalHomeLoanBankAdvances	2277000000	USD
	us-gaap	Payments For Federal Home Loan Bank Advances PaymentsForFederalHomeLoanBankAdvances	4677000000	USD
	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	222010000	USD
	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	36000000	USD
	us-gaap	Repayments Of Other Debt RepaymentsOfOtherDebt	9222000	USD
	us-gaap	Repayments Of Other Debt RepaymentsOfOtherDebt	100000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	75630000	USD
	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	81822000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	20000000	USD
	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	45380000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	2498000	USD
	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	2765000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	1835994000	USD
	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	326346000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	682572000	USD
	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	21018000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	247673000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	277587000	USD
CY2020Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	930245000	USD
CY2019Q3	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	298605000	USD
	us-gaap	Interest Paid Net InterestPaidNet	15913000	USD
CY2020Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	4081118000	USD
	us-gaap	Interest Paid Net InterestPaidNet	27623000	USD
	us-gaap	Income Taxes Paid IncomeTaxesPaid	32745000	USD
	us-gaap	Income Taxes Paid IncomeTaxesPaid	33134000	USD
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	1033000	USD
	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	386000	USD
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	301000	USD
	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	152000	USD
	colb	Changeindividendspayableonunvestedshares Changeindividendspayableonunvestedshares	522000	USD
	colb	Changeindividendspayableonunvestedshares Changeindividendspayableonunvestedshares	252000	USD
	us-gaap	Description Of New Accounting Pronouncements Not Yet Adopted DescriptionOfNewAccountingPronouncementsNotYetAdopted	<div style="margin-top:9pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Recently Issued Accounting Standards, Not Yet Adopted</span></div><div style="margin-top:9pt;text-indent:22.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">In March 2020, the FASB issued ASU 2020-04, </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Reference Rate Reform (Topic 848) - Facilitation of the Effects of Reference Rate Reform on Financial Reporting</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">. In response to concerns about structural risks of the cessation of LIBOR, the amendments in this ASU provide optional guidance for a limited time to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The amendments in this ASU provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments in this ASU apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. The expedients and exceptions provided by the amendments do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. The amendments in this ASU are elective and are effective March 12, 2020 for all entities. The adoption of this ASU is not expected to have a material impact on the Company’s Consolidated Financial Statements.</span></div><div style="margin-top:9pt;text-indent:22.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">In December 2019, the FASB issued ASU 2019-12, </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Income Taxes (Topic 740) - Simplifying the Accounting for Income Taxes. </span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The guidance issued in this ASU simplifies the accounting for income taxes by eliminating certain exceptions to the guidance in ASC 740 related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period and the recognition for deferred tax liabilities for outside basis differences. This ASU also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The ASU is effective for interim and annual reporting periods beginning after December 15, 2020; early adoption is permitted. The adoption of this ASU is not expected to have a material impact on the Company’s Consolidated Financial Statements.</span></div>
CY2020Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	205654000	USD
CY2020Q3	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	5052000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	4281720000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	3703096000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	63486000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	20440000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	3746142000	USD
CY2020Q3	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
CY2019Q3	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	0	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	194105000	USD
	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	259554000	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	0	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	435000	USD
CY2019Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3357000	USD
CY2020Q3	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	0	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	186000	USD
	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	1225000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	16425000	USD
	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2020Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	0	USD
CY2019Q3	us-gaap	Gain Loss On Investments GainLossOnInvestments	0	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	16674000	USD
	us-gaap	Gain Loss On Investments GainLossOnInvestments	2132000	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	16425000	USD
	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	-3000000	USD
	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
CY2020Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
CY2019Q3	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	13425000	USD
	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	92028000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	92931000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	595979000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	626018000	USD
CY2020Q3	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	4081118000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	2000662000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2133751000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	1392449000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	1429020000	USD
CY2020Q3	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	4281720000	USD
CY2020Q3	us-gaap	Debt Securities Available For Sale Restricted DebtSecuritiesAvailableForSaleRestricted	722227000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	580986000	USD
CY2020Q3	colb	Availableforsale Securities Continuous Unrealized Loss Position Lessthan12 Months Aggregate Loss Instant AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLossInstant	4212000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	23179000	USD
CY2020Q3	colb	Availableforsale Securities Continuous Unrealized Loss Position12 Monthsor Longer Aggregate Lossinstant AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLossinstant	840000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	604165000	USD
CY2020Q3	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	5052000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	1157774000	USD
CY2019Q4	colb	Availableforsale Securities Continuous Unrealized Loss Position Lessthan12 Months Aggregate Loss Instant AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLossInstant	13446000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	521420000	USD
CY2019Q4	colb	Availableforsale Securities Continuous Unrealized Loss Position12 Monthsor Longer Aggregate Lossinstant AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLossinstant	6994000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	1679194000	USD
CY2019Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	20440000	USD
CY2020Q2	colb	Visa Class Bsharessharessold VisaClassBsharessharessold	17360	shares
CY2020Q2	colb	Visa Class Bsharesgainonsale VisaClassBsharesgainonsale	3000000.0	USD
CY2020Q3	colb	Visa Class Bsharesremainingshares VisaClassBsharesremainingshares	77683	shares
CY2020Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	13400000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9688947000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	8743465000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	156968000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	9531979000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	8659497000	USD
CY2020Q3	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	24407000	USD
CY2019Q4	us-gaap	Loans Receivable Held For Sale Net Not Part Of Disposal Group LoansReceivableHeldForSaleNetNotPartOfDisposalGroup	17718000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	9625411000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	16305000	USD
CY2020Q3	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	47231000	USD
CY2020Q3	us-gaap	Notes Receivable Gross NotesReceivableGross	9688947000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	8686523000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	23882000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	33060000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	8743465000	USD
CY2020Q3	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	393000	USD
CY2019Q3	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	175000	USD
	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	1854000	USD
	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	1462000	USD
CY2020Q3	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	31879000	USD
CY2019Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	19275000	USD
CY2020Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	9	Modifications
CY2020Q3	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	4013000	USD
CY2020Q3	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	4013000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	11	Modifications
CY2019Q3	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	5384000	USD
CY2019Q3	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	5384000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	18	Modifications
	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	7066000	USD
	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	7066000	USD
	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	21	Modifications
	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	7253000	USD
	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	7253000	USD
CY2020Q3	colb	Financing Receivable Modifications Additional Commitment To Lend FinancingReceivableModificationsAdditionalCommitmentToLend	641000	USD
CY2019Q4	colb	Financing Receivable Modifications Additional Commitment To Lend FinancingReceivableModificationsAdditionalCommitmentToLend	1100000	USD
CY2020Q3	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
CY2019Q3	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	contract
CY2019Q3	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	26000	USD
	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	26000	USD
	colb	Loan Modifications Short Term Deferments Not Classified As Tdr Number Of Contracts LoanModificationsShortTermDefermentsNotClassifiedAsTDRNumberOfContracts	103	contract
	colb	Loan Modifications Short Term Deferments Not Classified As Tdr Net Of Unearned Income LoanModificationsShortTermDefermentsNotClassifiedAsTDRNetOfUnearnedIncome	114400000	USD
CY2020Q3	colb	Paycheck Protection Program Pp Ploansnetofunearnedincome PaycheckProtectionProgramPPPloansnetofunearnedincome	953200000	USD
CY2020Q3	colb	Minimumloanbalanceofnonaccrualcollateraldependentloansconsideredfor Acl MinimumloanbalanceofnonaccrualcollateraldependentloansconsideredforACL	500000	USD
CY2020Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	151546000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	4582000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	2604000	USD
CY2020Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	7400000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	156968000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2020Q1	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	85600000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	17011000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	5979000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	82400000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	156968000	USD
CY2019Q2	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	80517000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	3372000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	5216000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	299000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	82660000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83369000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	11647000	USD
	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	9059000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1879000	USD
CY2019Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	82660000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses Period Increase Decrease FinancingReceivableAllowanceForCreditLossesPeriodIncreaseDecrease	73000000.0	USD
CY2020Q2	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	8800000	USD
CY2019Q2	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	3980000	USD
CY2019Q4	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	3430000	USD
CY2018Q4	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	4330000	USD
CY2020Q3	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	800000	USD
CY2019Q3	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	-400000	USD
	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	4600000	USD
	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	-750000	USD
CY2020Q3	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	9600000	USD
CY2019Q3	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	3580000	USD
CY2020Q3	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	9600000	USD
CY2019Q3	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	3580000	USD
CY2020Q3	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	2017963000	USD
CY2020Q3	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	1494480000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	1076250000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	938911000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	871129000	USD
CY2020Q3	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	1560910000	USD
CY2020Q3	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	1696730000	USD
CY2020Q3	colb	Financing Receivable Revolving Convertedto Term Loans FinancingReceivableRevolvingConvertedtoTermLoans	32574000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9688947000	USD
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	156968000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	9531979000	USD
CY2019Q4	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	1594130000	USD
CY2019Q4	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	1280086000	USD
CY2019Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	1125520000	USD
CY2019Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	1023452000	USD
CY2019Q4	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	687055000	USD
CY2019Q4	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	1241613000	USD
CY2019Q4	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	1713819000	USD
CY2019Q4	colb	Financing Receivable Revolving Convertedto Term Loans FinancingReceivableRevolvingConvertedtoTermLoans	77790000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	8743465000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	8659497000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	6382000	USD
CY2020Q2	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	747000	USD
CY2019Q2	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	1118000	USD
CY2019Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	552000	USD
CY2018Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	6019000	USD
CY2020Q3	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	475000	USD
CY2019Q3	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	0	USD
	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	1033000	USD
	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	386000	USD
CY2020Q3	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	0	USD
CY2019Q3	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	0	USD
	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	0	USD
	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	195000	USD
CY2020Q3	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	681000	USD
CY2019Q3	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	588000	USD
	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	1026000	USD
CY2020Q3	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	82000	USD
CY2019Q3	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	95000	USD
	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	64000	USD
	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	797000	USD
CY2020Q3	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	623000	USD
CY2019Q3	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	625000	USD
CY2020Q3	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	623000	USD
CY2019Q3	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	625000	USD
CY2020Q3	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	436000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	765842000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	765842000	USD
CY2020Q3	us-gaap	Goodwill Goodwill	765842000	USD
CY2019Q3	us-gaap	Goodwill Goodwill	765842000	USD
CY2020Q3	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2019Q3	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2020Q3	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2019Q3	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2020Q3	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	28745000	USD
CY2019Q3	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	37908000	USD
CY2020Q3	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	28745000	USD
CY2019Q3	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	37908000	USD
CY2020Q3	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	794587000	USD
CY2019Q3	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	803750000	USD
CY2020Q3	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	794587000	USD
CY2019Q3	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	803750000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	2012000	USD
	us-gaap	Treasury Stock Shares Acquired TreasuryStockSharesAcquired	731000	shares
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	3432000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	7264000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	5880000	USD
CY2020Q3	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	4552000	USD
CY2020Q3	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	15000000.0	USD
CY2020Q3	us-gaap	Interest Rate Cash Flow Hedge Gain Loss To Be Reclassified During Next12 Months Net InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet	10700000	USD
CY2020Q3	us-gaap	Unrealized Gain Loss On Interest Rate Cash Flow Hedges Pretax Accumulated Other Comprehensive Income Loss UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss	-81000	USD
CY2019Q3	us-gaap	Unrealized Gain Loss On Interest Rate Cash Flow Hedges Pretax Accumulated Other Comprehensive Income Loss UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss	4088000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	2673000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	76000	USD
	us-gaap	Unrealized Gain Loss On Interest Rate Cash Flow Hedges Pretax Accumulated Other Comprehensive Income Loss UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss	26744000	USD
	us-gaap	Unrealized Gain Loss On Interest Rate Cash Flow Hedges Pretax Accumulated Other Comprehensive Income Loss UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss	19779000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	5803000	USD
	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Before Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax	76000	USD
CY2020Q3	colb	Repurchaseagreementsamountsoffsetinbalancesheet Repurchaseagreementsamountsoffsetinbalancesheet	0	USD
CY2020Q3	colb	Repurchaseagreementsnetamountpresentedinstatementoffinancialposition Repurchaseagreementsnetamountpresentedinstatementoffinancialposition	26966000	USD
CY2020Q3	us-gaap	Securities Sold Under Agreements To Repurchase Collateral Right To Reclaim Securities SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimSecurities	26966000	USD
CY2020Q3	colb	Securitiessoldunderagreementstorepurchaseamountnotoffset Securitiessoldunderagreementstorepurchaseamountnotoffset	0	USD
CY2019Q4	colb	Repurchaseagreementsamountsoffsetinbalancesheet Repurchaseagreementsamountsoffsetinbalancesheet	0	USD
CY2019Q4	colb	Repurchaseagreementsnetamountpresentedinstatementoffinancialposition Repurchaseagreementsnetamountpresentedinstatementoffinancialposition	64437000	USD
CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase Collateral Right To Reclaim Securities SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimSecurities	64437000	USD
CY2019Q4	colb	Securitiessoldunderagreementstorepurchaseamountnotoffset Securitiessoldunderagreementstorepurchaseamountnotoffset	0	USD
CY2020Q3	us-gaap	Secured Borrowings Gross Including Not Subject To Master Netting Arrangement SecuredBorrowingsGrossIncludingNotSubjectToMasterNettingArrangement	26966000	USD
CY2020Q3	us-gaap	Secured Borrowings Gross Difference Amount SecuredBorrowingsGrossDifferenceAmount	0	USD
CY2020Q3	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	27.36
CY2020Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	181077000	USD
CY2020Q1	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.28
CY2020Q1	colb	Common Stock Special Cash Dividends Per Share Declared CommonStockSpecialCashDividendsPerShareDeclared	0.22
CY2020Q2	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.28
CY2020Q2	colb	Common Stock Special Cash Dividends Per Share Declared CommonStockSpecialCashDividendsPerShareDeclared	0
CY2020Q3	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.28
CY2020Q3	colb	Common Stock Special Cash Dividends Per Share Declared CommonStockSpecialCashDividendsPerShareDeclared	0
CY2020Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-1504000	USD
CY2020Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	1972000	USD
CY2020Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-3476000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	177601000	USD
CY2019Q2	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	47150000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	17730000	USD
CY2019Q3	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-4000	USD
CY2019Q3	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	17734000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	64884000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	40367000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	141640000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	4406000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	137234000	USD
CY2020Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	177601000	USD
CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-35305000	USD
	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	101699000	USD
	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	1510000	USD
	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	100189000	USD
CY2019Q3	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	64884000	USD
CY2020Q3	colb	Visa Class Bsharesremainingshares VisaClassBsharesremainingshares	77683	shares
CY2020Q2	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	13425000	USD
CY2019Q2	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
CY2019Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
CY2018Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
CY2020Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Upward Price Adjustment Annual Amount EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount	0	USD
CY2019Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Upward Price Adjustment Annual Amount EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount	0	USD
	us-gaap	Equity Securities Without Readily Determinable Fair Value Upward Price Adjustment Annual Amount EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount	13425000	USD
	us-gaap	Equity Securities Without Readily Determinable Fair Value Upward Price Adjustment Annual Amount EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount	0	USD
CY2020Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	13425000	USD
CY2019Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
CY2020Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	13425000	USD
CY2019Q3	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	44734000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	50727000	USD
	us-gaap	Net Income Loss NetIncomeLoss	95944000	USD
	us-gaap	Net Income Loss NetIncomeLoss	148322000	USD
CY2020Q3	colb	Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares	164000	USD
CY2019Q3	colb	Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares	358000	USD
	colb	Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares	487000	USD
	colb	Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares Earningsallocatedtoparticipatingsecuritiesnonvestedrestrictedshares	1204000	USD
CY2020Q3	colb	Basic Earnings Allocated To Common Shareholders BasicEarningsAllocatedToCommonShareholders	44570000	USD
CY2019Q3	colb	Basic Earnings Allocated To Common Shareholders BasicEarningsAllocatedToCommonShareholders	50369000	USD
	colb	Basic Earnings Allocated To Common Shareholders BasicEarningsAllocatedToCommonShareholders	95457000	USD
	colb	Basic Earnings Allocated To Common Shareholders BasicEarningsAllocatedToCommonShareholders	147118000	USD
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70726000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	71803000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70870000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72256000	shares
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.63
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.70
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.35
	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.04
CY2020Q3	colb	Diluted Earnings Allocated To Common Shareholders DilutedEarningsAllocatedToCommonShareholders	44570000	USD
CY2019Q3	colb	Diluted Earnings Allocated To Common Shareholders DilutedEarningsAllocatedToCommonShareholders	50369000	USD
	colb	Diluted Earnings Allocated To Common Shareholders DilutedEarningsAllocatedToCommonShareholders	95457000	USD
	colb	Diluted Earnings Allocated To Common Shareholders DilutedEarningsAllocatedToCommonShareholders	147118000	USD
CY2020Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70726000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	71803000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70870000	shares
	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72256000	shares
CY2020Q3	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	36000	shares
CY2019Q3	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	0	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	36000	shares
	us-gaap	Weighted Average Number Diluted Shares Outstanding Adjustment WeightedAverageNumberDilutedSharesOutstandingAdjustment	1000	shares
CY2020Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	70762000	shares
CY2019Q3	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	71803000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	70906000	shares
	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72257000	shares
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.63
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.70
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.35
	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.04
CY2020Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	596000	shares
CY2019Q3	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	487000	shares
	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	0	shares
CY2020Q3	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	6658000	USD
CY2019Q3	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	9015000	USD
	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	20538000	USD
	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	27030000	USD
CY2020Q3	colb	Cardrevenue Cardrevenue	3834000	USD
	us-gaap	Noninterest Income NoninterestIncome	80938000	USD
CY2019Q3	colb	Cardrevenue Cardrevenue	4006000	USD
	colb	Cardrevenue Cardrevenue	10431000	USD
	colb	Cardrevenue Cardrevenue	11431000	USD
CY2020Q3	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	3253000	USD
CY2019Q3	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	3226000	USD
	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	9481000	USD
	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	9608000	USD
CY2020Q3	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	13745000	USD
CY2019Q3	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	16247000	USD
	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	40450000	USD
	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	48069000	USD
CY2020Q3	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	8727000	USD
CY2019Q3	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	11783000	USD
	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	40488000	USD
	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	27305000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	22472000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	28030000	USD
	us-gaap	Noninterest Income NoninterestIncome	75374000	USD

Files In Submission

Name	View Source	Status
0000887343-20-000210-index-headers.html	Edgar Link	pending
0000887343-20-000210-index.html	Edgar Link	pending
0000887343-20-000210.txt	Edgar Link	pending
0000887343-20-000210-xbrl.zip	Edgar Link	pending
colb-20200930.htm	Edgar Link	pending
colb-20200930.xsd	Edgar Link	pending
colb-20200930_cal.xml	Edgar Link	unprocessable
colb-20200930_def.xml	Edgar Link	unprocessable
colb-20200930_htm.xml	Edgar Link	completed
colb-20200930_lab.xml	Edgar Link	unprocessable
colb-20200930_pre.xml	Edgar Link	unprocessable
colb3q2020ex311.htm	Edgar Link	pending
colb3q2020ex312.htm	Edgar Link	pending
colb3q2020ex32.htm	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
R1.htm	Edgar Link	pending
R10.htm	Edgar Link	pending
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report.css	Edgar Link	pending
Show.js	Edgar Link	pending

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$COLB
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2020 Q4 Form 10-Q Financial Statement

#000088734320000210 Filed on November 05, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$COLB Columbia Banking System Inc Stock $colb

2020 Q4 Form 10-Q Financial Statement

#000088734320000210 Filed on November 05, 2020

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$COLB
Columbia Banking System Inc Stock $colb