$COLB
Columbia Banking System Inc Stock $colb

$colb Overview Financials Valuation SEC Filings Company Website

2020 Q4 Form 10-K Financial Statement

#000088734321000065 Filed on February 26, 2021

Income Statement

Concept	2020 Q4	2020 Q3	2020 Q2
Revenue	$133.3M	$127.4M	$126.2M
YoY Change	0.14%	-3.89%	-6.79%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development		$7.095M	$7.981M
YoY Change		39.06%	73.46%
% of Gross Profit
Depreciation & Amortization	$400.0K	$4.100M	-$2.800M
YoY Change	-95.0%	-53.93%	-130.77%
% of Gross Profit
Operating Expenses		$7.095M	$7.981M
YoY Change		39.06%	73.46%
Operating Profit
YoY Change
Interest Expense	$2.184M	$2.658M	$4.381M
YoY Change	-73.66%	-73.64%	-57.49%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$75.07M	$54.68M	$44.78M
YoY Change	29.37%	-13.35%	-29.84%
Income Tax	$16.77M	$9.949M	$8.195M
% Of Pretax Income	22.34%	18.19%	18.3%
Net Earnings	$58.30M	$44.73M	$36.58M
YoY Change	26.38%	-11.81%	-29.27%
Net Earnings / Revenue	43.74%	35.12%	28.98%
Basic Earnings Per Share	$0.82	$0.63	$0.52
Diluted Earnings Per Share	$0.82	$0.63	$0.52
COMMON SHARES
Basic Shares Outstanding	71.61M shares	70.73M shares	70.68M shares
Diluted Shares Outstanding		70.76M shares	70.71M shares

Balance Sheet

Concept	2020 Q4	2020 Q3	2020 Q2
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$653.8M	$930.2M	$1.098B
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	$164.4M
YoY Change	-2.02%	-0.84%	-1.75%
Goodwill	$765.8M	$765.8M	$765.8M
YoY Change	0.0%	0.0%	0.0%
Intangibles	$26.73M	$28.75M	$30.94M
YoY Change	-24.6%	-24.17%	-23.69%
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	$15.92B
YoY Change	17.79%	17.99%	21.62%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable
YoY Change
Accrued Expenses
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt	$74.00M	$27.00M	$51.00M
YoY Change	15.63%	12.5%	2.0%
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$74.00M	$27.00M	$51.00M
YoY Change	17.46%	-52.63%	-5.56%
LONG-TERM LIABILITIES
Long-Term Debt	$35.00M	$35.00M	$35.00M
YoY Change	0.0%	0.0%	0.0%
Other Long-Term Liabilities	$251.0M	$262.0M	$269.0M
YoY Change	110.92%	100.0%	142.34%
Total Long-Term Liabilities	$286.0M	$297.0M	$304.0M
YoY Change	85.71%	78.92%	108.22%
TOTAL LIABILITIES
Total Short-Term Liabilities	$74.00M	$27.00M	$51.00M
Total Long-Term Liabilities	$286.0M	$297.0M	$304.0M
Total Liabilities	$14.24B	$13.93B	$13.64B
YoY Change	19.44%	20.14%	24.52%
SHAREHOLDERS EQUITY
Retained Earnings	$575.2M	$537.0M	$512.4M
YoY Change	10.69%	8.76%	10.56%
Common Stock	$1.661B	$1.658B	$1.654B
YoY Change	0.62%	0.6%	0.56%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$70.83M	$70.83M	$70.83M
YoY Change	39.34%	56.09%	223.99%
Treasury Stock Shares	2.184M shares	2.184M shares	2.184M shares
Shareholders Equity	$2.348B	$2.302B	$2.277B
YoY Change
Total Liabilities & Shareholders Equity	$16.58B	$16.23B	$15.92B
YoY Change	17.79%	17.99%	21.62%

Cashflow Statement

Concept	2020 Q4	2020 Q3	2020 Q2
OPERATING ACTIVITIES
Net Income	$58.30M	$44.73M	$36.58M
YoY Change	26.38%	-11.81%	-29.27%
Depreciation, Depletion And Amortization	$400.0K	$4.100M	-$2.800M
YoY Change	-95.0%	-53.93%	-130.77%
Cash From Operating Activities	$48.50M	$60.70M	$17.70M
YoY Change	-2.81%	7.82%	-61.52%
INVESTING ACTIVITIES
Capital Expenditures	-$1.200M	-$3.000M	-$2.800M
YoY Change	-53.85%	30.43%	64.71%
Acquisitions
YoY Change
Other Investing Activities	-$620.4M	-$500.6M	-$894.0M
YoY Change	54.06%	-14.7%	-1211.94%
Cash From Investing Activities	-$621.6M	-$503.6M	-$896.8M
YoY Change	53.33%	-14.53%	-1239.52%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	296.6M	275.5M	1.761B
YoY Change	-2.59%	-51.9%	-2354.8%
NET CHANGE
Cash From Operating Activities	48.50M	60.70M	17.70M
Cash From Investing Activities	-621.6M	-503.6M	-896.8M
Cash From Financing Activities	296.6M	275.5M	1.761B
Net Change In Cash	-276.5M	-167.4M	881.9M
YoY Change	442.16%	-519.55%	1792.49%
FREE CASH FLOW
Cash From Operating Activities	$48.50M	$60.70M	$17.70M
Capital Expenditures	-$1.200M	-$3.000M	-$2.800M
Free Cash Flow	$49.70M	$63.70M	$20.50M
YoY Change	-5.33%	8.7%	-57.02%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2020	dei	Amendment Flag AmendmentFlag	false
CY2020	dei	Document Type DocumentType	10-K
CY2020	dei	Document Annual Report DocumentAnnualReport	true
CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	000-20288
CY2020	dei	Entity Registrant Name EntityRegistrantName	COLUMBIA BANKING SYSTEM, INC.
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	WA
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	91-1422237
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CY2020	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-315000	USD
CY2019	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	-692000	USD
CY2018	colb	Netcostbenefitofoperationofotherrealestateowned Netcostbenefitofoperationofotherrealestateowned	1218000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	36455000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	34152000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	37024000	USD
CY2020	us-gaap	Noninterest Expense NoninterestExpense	334519000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	345482000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	340490000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	192392000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	241611000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	211836000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38148000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	47160000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38954000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	154244000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	194451000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	172882000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.17
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.68
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.36
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.68
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.36
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	70835000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	71999000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72385000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	70880000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72032000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72390000	shares
CY2020	us-gaap	Net Income Loss NetIncomeLoss	154244000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	194451000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	172882000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-39489000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	-20540000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax	4067000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	130355000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	67802000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax	-13425000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	66000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	496000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax	25000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	219000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	1636000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Net Of Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax	81000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	130136000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	66166000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-13506000	USD
CY2020	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	659000	USD
CY2019	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	619000	USD
CY2018	us-gaap	Other Comprehensive Income Defined Benefit Plans Net Unamortized Gain Loss Arising During Period Tax OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax	-7000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax	2177000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax	2042000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Reclassification Adjustments Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax	-24000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-96000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-74000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Amortization Adjustment From Aoci Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditTax	-74000	USD
CY2020	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	318000	USD
CY2019	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	245000	USD
CY2018	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	245000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	1859000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	1797000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax	-269000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-6062000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	-3562000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	20012000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	11760000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	1957000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	138000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	6461000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	457000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Reclassification After Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	13551000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	11303000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	0	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	141828000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	75672000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-13237000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	296072000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	270123000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	159645000	USD
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	1949922000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	172882000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-13237000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	1857000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	8354000	USD
CY2018	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	7000	USD
CY2018	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	7000	USD
CY2018	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2677000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.14
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	83459000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	2033649000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	194451000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	75672000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	2025000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	9271000	USD
CY2019	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	3000	USD
CY2019	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2792000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.40
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	102265000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	50834000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	2159962000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	154244000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	141828000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	2028000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	10737000	USD
CY2020	colb	Stock Adjustment Value Deferred Compensation StockAdjustmentValueDeferredCompensation	2000	USD
CY2020	us-gaap	Stock Repurchased And Retired During Period Value StockRepurchasedAndRetiredDuringPeriodValue	2522000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.34
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	96215000	USD
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	20000000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	2347607000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	154244000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	194451000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	172882000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	77700000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3493000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	14769000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	10737000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	9271000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	8354000	USD
CY2020	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	14893000	USD
CY2019	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	34213000	USD
CY2018	us-gaap	Depreciation Amortization And Accretion Net DepreciationAmortizationAndAccretionNet	32971000	USD
CY2020	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	16710000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	2132000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Gain Loss Net AvailableForSaleSecuritiesGrossRealizedGainLossNet	-89000	USD
CY2020	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	1334000	USD
CY2019	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	7317000	USD
CY2018	us-gaap	Gain Loss On Sale Of Other Assets GainLossOnSaleOfOtherAssets	-316000	USD
CY2020	colb	Netgainonsaleandvaluationadjustmentsof Oreo NetgainonsaleandvaluationadjustmentsofOREO	34000	USD
CY2019	colb	Netgainonsaleandvaluationadjustmentsof Oreo NetgainonsaleandvaluationadjustmentsofOREO	602000	USD
CY2018	colb	Netgainonsaleandvaluationadjustmentsof Oreo NetgainonsaleandvaluationadjustmentsofOREO	-1218000	USD
CY2020	us-gaap	Gain Loss On Sale Of Insurance Block GainLossOnSaleOfInsuranceBlock	0	USD
CY2019	us-gaap	Gain Loss On Sale Of Insurance Block GainLossOnSaleOfInsuranceBlock	3051000	USD
CY2018	us-gaap	Gain Loss On Sale Of Insurance Block GainLossOnSaleOfInsuranceBlock	0	USD
CY2020	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	491385000	USD
CY2019	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	210484000	USD
CY2018	us-gaap	Payments For Origination And Purchases Of Loans Held For Sale PaymentsForOriginationAndPurchasesOfLoansHeldForSale	133945000	USD
CY2020	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	483130000	USD
CY2019	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	196615000	USD
CY2018	us-gaap	Proceeds From Sale Of Loans Held For Sale ProceedsFromSaleOfLoansHeldForSale	135862000	USD
CY2020	us-gaap	Increase Decrease In Mortgage Loans Held For Sale IncreaseDecreaseInMortgageLoansHeldForSale	508000	USD
CY2019	us-gaap	Increase Decrease In Mortgage Loans Held For Sale IncreaseDecreaseInMortgageLoansHeldForSale	0	USD
CY2018	us-gaap	Increase Decrease In Mortgage Loans Held For Sale IncreaseDecreaseInMortgageLoansHeldForSale	0	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-13768000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	330000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	108000	USD
CY2020	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	7992000	USD
CY2019	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	1516000	USD
CY2018	us-gaap	Increase Decrease In Interest And Dividends Receivable IncreaseDecreaseInInterestAndDividendsReceivable	4442000	USD
CY2020	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	-933000	USD
CY2019	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	632000	USD
CY2018	us-gaap	Increase Decrease In Interest Payable Net IncreaseDecreaseInInterestPayableNet	164000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	48539000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	23464000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-2176000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	32791000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	14308000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	6679000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	192292000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	204747000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	237201000	USD
CY2020	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	619543000	USD
CY2018	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	-2069000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	2118667000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	1196895000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	291857000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities PaymentsToAcquireAvailableForSaleSecurities	965585000	USD
CY2020	us-gaap	Payments To Acquire Loans Receivable PaymentsToAcquireLoansReceivable	50035000	USD
CY2019	us-gaap	Payments To Acquire Loans Receivable PaymentsToAcquireLoansReceivable	57075000	USD
CY2018	us-gaap	Payments To Acquire Loans Receivable PaymentsToAcquireLoansReceivable	46969000	USD
CY2020	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8720000	USD
CY2019	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	8447000	USD
CY2018	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	11328000	USD
CY2020	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	53240000	USD
CY2019	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	273800000	USD
CY2018	us-gaap	Payments To Acquire Federal Home Loan Bank Stock PaymentsToAcquireFederalHomeLoanBankStock	197440000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	194697000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	259554000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	32330000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Equity ProceedsFromSaleOfAvailableForSaleSecuritiesEquity	3000000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Equity ProceedsFromSaleOfAvailableForSaleSecuritiesEquity	0	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Equity ProceedsFromSaleOfAvailableForSaleSecuritiesEquity	4808000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	603129000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	428025000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	465747000	USD
CY2020	colb	Proceeds From Sales Of Loans Held For Investment And Other Assets ProceedsFromSalesOfLoansHeldForInvestmentAndOtherAssets	2948000	USD
CY2019	colb	Proceeds From Sales Of Loans Held For Investment And Other Assets ProceedsFromSalesOfLoansHeldForInvestmentAndOtherAssets	8634000	USD
CY2018	colb	Proceeds From Sales Of Loans Held For Investment And Other Assets ProceedsFromSalesOfLoansHeldForInvestmentAndOtherAssets	16030000	USD
CY2020	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	91080000	USD
CY2019	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	251640000	USD
CY2018	us-gaap	Proceeds From Sale Of Federal Home Loan Bank Stock ProceedsFromSaleOfFederalHomeLoanBankStock	181920000	USD
CY2020	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	1074000	USD
CY2019	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	6506000	USD
CY2018	us-gaap	Proceeds From Sale Of Foreclosed Assets ProceedsFromSaleOfForeclosedAssets	7261000	USD
CY2020	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1050000	USD
CY2020	colb	Proceeds From Termination Of Cash Flow Hedging Instrument ProceedsFromTerminationOfCashFlowHedgingInstrument	34442000	USD
CY2019	colb	Proceeds From Termination Of Cash Flow Hedging Instrument ProceedsFromTerminationOfCashFlowHedgingInstrument	0	USD
CY2018	colb	Proceeds From Termination Of Cash Flow Hedging Instrument ProceedsFromTerminationOfCashFlowHedgingInstrument	0	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	8265000	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	5074000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-1918785000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-865450000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-506083000	USD
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	3185167000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	226958000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-73591000	USD
CY2020	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	9422000	USD
CY2019	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	3343000	USD
CY2018	us-gaap	Increase Decrease In Federal Funds Purchased And Securities Sold Under Agreements To Repurchase Net IncreaseDecreaseInFederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseNet	7035000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2028000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	2025000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1857000	USD
CY2020	us-gaap	Proceeds From Federal Home Loan Bank Advances ProceedsFromFederalHomeLoanBankAdvances	1331000000	USD
CY2019	us-gaap	Proceeds From Federal Home Loan Bank Advances ProceedsFromFederalHomeLoanBankAdvances	6845000000	USD
CY2018	us-gaap	Proceeds From Federal Home Loan Bank Advances ProceedsFromFederalHomeLoanBankAdvances	4936000000	USD
CY2020	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	222010000	USD
CY2019	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	36000000	USD
CY2018	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	5010000	USD
CY2020	us-gaap	Proceeds From Other Debt ProceedsFromOtherDebt	9222000	USD
CY2019	us-gaap	Proceeds From Other Debt ProceedsFromOtherDebt	100000	USD
CY2018	us-gaap	Proceeds From Other Debt ProceedsFromOtherDebt	0	USD
CY2020	us-gaap	Payments For Federal Home Loan Bank Advances PaymentsForFederalHomeLoanBankAdvances	2277000000	USD
CY2019	us-gaap	Payments For Federal Home Loan Bank Advances PaymentsForFederalHomeLoanBankAdvances	6291000000	USD
CY2018	us-gaap	Payments For Federal Home Loan Bank Advances PaymentsForFederalHomeLoanBankAdvances	4548000000	USD
CY2020	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	222010000	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	36000000	USD
CY2018	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	5010000	USD
CY2020	us-gaap	Repayments Of Other Debt RepaymentsOfOtherDebt	9222000	USD
CY2019	us-gaap	Repayments Of Other Debt RepaymentsOfOtherDebt	100000	USD
CY2018	us-gaap	Repayments Of Other Debt RepaymentsOfOtherDebt	0	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	95509000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	101911000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	83440000	USD
CY2020	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	USD
CY2019	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	USD
CY2018	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	8248000	USD
CY2020	colb	Repaymentoftermrepurchaseagreement Repaymentoftermrepurchaseagreement	0	USD
CY2019	colb	Repaymentoftermrepurchaseagreement Repaymentoftermrepurchaseagreement	0	USD
CY2018	colb	Repaymentoftermrepurchaseagreement Repaymentoftermrepurchaseagreement	25000000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	20000000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	50834000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	0	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	2522000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	2792000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	2677000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	2132586000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	630789000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	203936000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	406093000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-29914000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-64946000	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
CY2017Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	342533000	USD
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	653766000	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
CY2020	us-gaap	Interest Paid Net InterestPaidNet	18631000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	35916000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	18066000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	43287000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	47375000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	24067000	USD
CY2020	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	1033000	USD
CY2019	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	386000	USD
CY2020	colb	Number Of Days Used To Determine Treatment As Cash Equivalent NumberOfDaysUsedToDetermineTreatmentAsCashEquivalent	90
CY2018	us-gaap	Transfer To Other Real Estate TransferToOtherRealEstate	1200000	USD
CY2020	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	302000	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	451000	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	195000	USD
CY2020	colb	Changeindividendspayableonunvestedshares Changeindividendspayableonunvestedshares	706000	USD
CY2019	colb	Changeindividendspayableonunvestedshares Changeindividendspayableonunvestedshares	354000	USD
CY2018	colb	Changeindividendspayableonunvestedshares Changeindividendspayableonunvestedshares	19000	USD
CY2020Q4	colb	Number Of Branch Locations NumberOfBranchLocations	145	location
CY2020Q4	colb	Fhl Bmembershipstockpurchaserequirementcap FHLBmembershipstockpurchaserequirementcap	10000000	USD
CY2020Q4	colb	Federal Home Loan Bankstockparvalue FederalHomeLoanBankstockparvalue	100	USD
CY2020	colb	Numberof Daysof Delinquencyat Which Loans Are Categorized As Non Accrual Status NumberofDaysofDelinquencyatWhichLoansAreCategorizedAsNonAccrualStatus	90
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Policy For Uncollectible Amounts FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts	<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%">Allowance for Credit Losses</span></div><div style="margin-top:9pt;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">In accordance with ASU 2016-13, the Company adopted ASC 326 as of January 1, 2020. The allowance for credit losses under ASC 326 is an accounting estimate of expected losses over the contractual life of assets carried at amortized cost within the Company’s loan portfolio at the balance sheet date. The ASU requires a financial asset (or group of financial assets) measured at amortized cost to be presented at the net amount expected to be collected. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset to present the net carrying value at the amount expected to be collected on the financial asset.</span></div><div style="margin-top:9pt;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The quantitative allowance is calculated using a DCF approach with a probability of default methodology. The probability of default is an assumption derived from regression models which determines the relationship between historical defaults and certain economic variables. The Company determines a reasonable and supportable forecast and applies that forecast to the regression model to determine defaults over the forecast period. The Company leverages economic projections from an independent third-party provider on a quarterly basis that are vetted by the Company through quantifiable analysis and comparisons are evaluated by a committee before a final scenario is determined for the 18 month reasonable and supportable forecast period used by the Company. Following the forecast period, the economic variables used to calculate the probability of default revert to a historical average at a constant rate. Other assumptions relevant to the discounted cash flow model to derive the quantitative allowance include the loss given default, which is the estimate of loss for a defaulted loan, and the discount rate applied to future cash flows. The DCF model calculates the net present value of each loan using both the contractual and expected cash flows, respectively.</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 addition to the quantitative portion of the allowance for credit losses, the Company also considers the effects of the following qualitative factors in its calculation of expected losses in the loan portfolio:</span></div><div style="margin-top:9pt;padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Economic and business conditions;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Concentration of credit;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Lending management and staff;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Lending policies and procedures;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Loss and recovery trends;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Nature and volume of the portfolio;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Trends in problem loans, loan delinquencies and nonaccrual loans;</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Quality of internal loan review; and</span></div><div style="padding-left:49.5pt;text-indent:-13.5pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">•</span><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%;padding-left:10pt">Other external factors such as the effect of economic stimulus and loan modification programs.</span></div><div style="margin-top:9pt;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The qualitative factor methodology is based on quantitative metrics, but also includes a high degree of subjectivity and changes in any of the metrics could have a significant impact on our calculation of the allowance. </span></div>Loans for which repayment is expected to be provided substantially through the operation or sale of collateral are considered collateral-dependent. The allowance for credit losses for collateral-dependent loans is measured on the basis of the fair value of the collateral when foreclosure is probable.
CY2020Q4	colb	Number Of Issuances Of Securities Exceeding Shareholders Equity Threshold NumberOfIssuancesOfSecuritiesExceedingShareholdersEquityThreshold	0	issuance
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	4997529000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	219873000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	7268000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5210134000	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
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	194697000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	259554000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	32330000	USD
CY2020	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	471000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	3357000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Gains AvailableForSaleSecuritiesGrossRealizedGains	235000	USD
CY2020	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	186000	USD
CY2019	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	1225000	USD
CY2018	us-gaap	Available For Sale Securities Gross Realized Losses AvailableForSaleSecuritiesGrossRealizedLosses	129000	USD
CY2020	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	16425000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	-195000	USD
CY2020	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	16710000	USD
CY2019	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	2132000	USD
CY2018	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-89000	USD
CY2020	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	16425000	USD
CY2019	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Gain Loss EquitySecuritiesFvNiGainLoss	-195000	USD
CY2020	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	-3000000	USD
CY2019	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain Loss EquitySecuritiesFvNiRealizedGainLoss	195000	USD
CY2020	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	13425000	USD
CY2019	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
CY2018	us-gaap	Equity Securities Fv Ni Unrealized Gain Loss EquitySecuritiesFvNiUnrealizedGainLoss	0	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	69317000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	69895000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	713669000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	752119000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	2295998000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	2431876000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	1918545000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	1956244000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	4997529000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	5210134000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Restricted DebtSecuritiesAvailableForSaleRestricted	861574000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Restricted DebtSecuritiesAvailableForSaleRestricted	588573000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	880507000	USD
CY2020Q4	colb	Availableforsale Securities Continuous Unrealized Loss Position Lessthan12 Months Aggregate Loss Instant AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLossInstant	6453000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	18597000	USD
CY2020Q4	colb	Availableforsale Securities Continuous Unrealized Loss Position12 Monthsor Longer Aggregate Lossinstant AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLossinstant	815000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Fair Value AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue	899104000	USD
CY2020Q4	us-gaap	Available For Sale Securities Continuous Unrealized Loss Position Accumulated Loss AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	7268000	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
CY2020	colb	Visa Class Bsharessharessold VisaClassBsharessharessold	17360	shares
CY2020	colb	Visa Class Bsharesgainonsale VisaClassBsharesgainonsale	3000000.0	USD
CY2020Q4	colb	Visa Class Bsharesremainingshares VisaClassBsharesremainingshares	77683	shares
CY2020Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	13400000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9427660000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	8743465000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	149140000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	9278520000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	8659497000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	9364697000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	28157000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	34806000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	9427660000	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
CY2020	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	2000000	USD
CY2019	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	1671000	USD
CY2018	colb	Financing Receivable Accrued Interest Reversed Through Interest Income FinancingReceivableAccruedInterestReversedThroughInterestIncome	1564000	USD
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	20911000	USD
CY2019Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	19275000	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	19	Modifications
CY2020	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	7566000	USD
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	7566000	USD
CY2019	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	24	Modifications
CY2019	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	7348000	USD
CY2019	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	7348000	USD
CY2018	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	34	Modifications
CY2018	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	22047000	USD
CY2018	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	22047000	USD
CY2020Q4	colb	Financing Receivable Modifications Additional Commitment To Lend FinancingReceivableModificationsAdditionalCommitmentToLend	651000	USD
CY2019Q4	colb	Financing Receivable Modifications Additional Commitment To Lend FinancingReceivableModificationsAdditionalCommitmentToLend	1100000	USD
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	1	contract
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	26000	USD
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Number Of Contracts1 FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1	0	contract
CY2020	colb	Loan Modifications Short Term Deferments Not Classified As Tdr Number Of Contracts LoanModificationsShortTermDefermentsNotClassifiedAsTDRNumberOfContracts	70	contract
CY2020	colb	Loan Modifications Short Term Deferments Not Classified As Tdr Net Of Unearned Income LoanModificationsShortTermDefermentsNotClassifiedAsTDRNetOfUnearnedIncome	146700000	USD
CY2020Q4	colb	Paycheck Protection Program Pp Ploansnetofunearnedincome PaycheckProtectionProgramPPPloansnetofunearnedincome	651600000	USD
CY2020Q4	colb	Minimumloanbalanceofnonaccrualcollateraldependentloansconsideredfor Acl MinimumloanbalanceofnonaccrualcollateraldependentloansconsideredforACL	500000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	21092000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	6932000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	77700000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	149140000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83369000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	15215000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	12321000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3493000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83968000	USD
CY2017Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	75646000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	18555000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	11509000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	14769000	USD
CY2018Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	83369000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Period Increase Decrease FinancingReceivableAllowanceForCreditLossesPeriodIncreaseDecrease	63500000	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
CY2017Q4	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	3130000	USD
CY2020	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	3300000	USD
CY2019	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	-900000	USD
CY2018	colb	Allowance For Loan And Lease Losses Net Changes In Unfunded Commitments And Letters Of Credit Allowance AllowanceForLoanAndLeaseLossesNetChangesInUnfundedCommitmentsAndLettersOfCreditAllowance	1200000	USD
CY2020Q4	colb	Allowance For Unfunded Loan Commitments And Letters Of Credit AllowanceForUnfundedLoanCommitmentsAndLettersOfCredit	8300000	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
CY2020Q4	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	2223383000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	1379336000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	985423000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	875545000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	812034000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	1413553000	USD
CY2020Q4	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	1687345000	USD
CY2020Q4	colb	Financing Receivable Revolving Convertedto Term Loans FinancingReceivableRevolvingConvertedtoTermLoans	51041000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	9427660000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	149140000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Reported Amount LoansAndLeasesReceivableNetReportedAmount	9278520000	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
CY2019Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	552000	USD
CY2018Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	6019000	USD
CY2020	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	1033000	USD
CY2019	colb	Real Estate Acquired Through Foreclosure Transfers In Net Of Write Downs RealEstateAcquiredThroughForeclosureTransfersInNetOfWriteDowns	386000	USD
CY2020	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	70000	USD
CY2019	colb	Transfer Other Real Estate Write Down TransferOtherRealEstateWriteDown	195000	USD
CY2020	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	1066000	USD
CY2019	us-gaap	Proceeds From Sale Of Wholly Owned Real Estate And Real Estate Acquired In Settlement Of Loans ProceedsFromSaleOfWhollyOwnedRealEstateAndRealEstateAcquiredInSettlementOfLoans	6455000	USD
CY2020	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	104000	USD
CY2019	us-gaap	Gains Losses On Sales Of Other Real Estate GainsLossesOnSalesOfOtherRealEstate	797000	USD
CY2020Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	553000	USD
CY2019Q4	us-gaap	Real Estate Acquired Through Foreclosure RealEstateAcquiredThroughForeclosure	552000	USD
CY2020Q4	us-gaap	Mortgage Loans In Process Of Foreclosure Amount MortgageLoansInProcessOfForeclosureAmount	260000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	241153000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Gross PropertyPlantAndEquipmentGross	243329000	USD
CY2020Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	79094000	USD
CY2019Q4	us-gaap	Accumulated Depreciation Depletion And Amortization Property Plant And Equipment AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	77921000	USD
CY2020Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	162059000	USD
CY2019Q4	us-gaap	Property Plant And Equipment Net PropertyPlantAndEquipmentNet	165408000	USD
CY2020	us-gaap	Depreciation And Amortization DepreciationAndAmortization	10700000	USD
CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	10300000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	10400000	USD
CY2020Q4	us-gaap	Goodwill Goodwill	765842000	USD
CY2019Q4	us-gaap	Goodwill Goodwill	765842000	USD
CY2018Q4	us-gaap	Goodwill Goodwill	765842000	USD
CY2020Q4	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2019Q4	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2018Q4	us-gaap	Indefinite Lived Intangible Assets Excluding Goodwill IndefiniteLivedIntangibleAssetsExcludingGoodwill	919000	USD
CY2020Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	26734000	USD
CY2019Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	35458000	USD
CY2018Q4	us-gaap	Intangible Assets Net Excluding Goodwill IntangibleAssetsNetExcludingGoodwill	45937000	USD
CY2020Q4	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	792576000	USD
CY2019Q4	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	801300000	USD
CY2018Q4	colb	Goodwill And Intangible Assets Total GoodwillAndIntangibleAssetsTotal	811779000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Next Twelve Months FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths	7264000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Two FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo	5880000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Three FiniteLivedIntangibleAssetsAmortizationExpenseYearThree	4552000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Four FiniteLivedIntangibleAssetsAmortizationExpenseYearFour	3432000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Amortization Expense Year Five FiniteLivedIntangibleAssetsAmortizationExpenseYearFive	2415000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P8Y2M12D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.026
CY2019	us-gaap	Operating Lease Payments OperatingLeasePayments	11200000	USD
CY2020	us-gaap	Operating Lease Payments OperatingLeasePayments	11200000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	13900000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	20600000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	11073000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	10851000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	1732000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	1805000	USD
CY2020	us-gaap	Sublease Income SubleaseIncome	1454000	USD
CY2019	us-gaap	Sublease Income SubleaseIncome	1182000	USD
CY2020	us-gaap	Lease Cost LeaseCost	11351000	USD
CY2019	us-gaap	Lease Cost LeaseCost	11474000	USD
CY2018	us-gaap	Operating Leases Rent Expense Sublease Rentals1 OperatingLeasesRentExpenseSubleaseRentals1	1200000	USD
CY2018	us-gaap	Operating Leases Rent Expense Net OperatingLeasesRentExpenseNet	9600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	11224000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	10860000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	9612000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	8689000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	7423000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	27354000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	75162000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	7659000	USD
CY2020Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	6913214000	USD
CY2019Q4	us-gaap	Noninterest Bearing Deposit Liabilities Domestic NoninterestBearingDepositLiabilitiesDomestic	5328146000	USD
CY2020Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	2780922000	USD
CY2019Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	2322644000	USD
CY2020Q4	us-gaap	Interest Bearing Domestic Deposit Demand InterestBearingDomesticDepositDemand	1433083000	USD
CY2019Q4	us-gaap	Interest Bearing Domestic Deposit Demand InterestBearingDomesticDepositDemand	1150437000	USD
CY2020Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	1169721000	USD
CY2019Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	882050000	USD
CY2020Q4	colb	Interestbearingpublicfundsotherthancertificatesofdeposit Interestbearingpublicfundsotherthancertificatesofdeposit	656273000	USD
CY2019Q4	colb	Interestbearingpublicfundsotherthancertificatesofdeposit Interestbearingpublicfundsotherthancertificatesofdeposit	301203000	USD
CY2020Q4	colb	Certificates Of Deposit Less Than250000 CertificatesOfDepositLessThan250000	201805000	USD
CY2019Q4	colb	Certificates Of Deposit Less Than250000 CertificatesOfDepositLessThan250000	218764000	USD
CY2020Q4	colb	Certificates Of Deposit250000 Or More CertificatesOfDeposit250000OrMore	108935000	USD
CY2019Q4	colb	Certificates Of Deposit250000 Or More CertificatesOfDeposit250000OrMore	151995000	USD
CY2020Q4	colb	Certificates Of Deposit Insured By Cdars CertificatesOfDepositInsuredByCdars	23105000	USD
CY2019Q4	colb	Certificates Of Deposit Insured By Cdars CertificatesOfDepositInsuredByCdars	17065000	USD
CY2020Q4	colb	Otherbrokeredcertificatesofdeposit Otherbrokeredcertificatesofdeposit	5000000	USD
CY2019Q4	colb	Otherbrokeredcertificatesofdeposit Otherbrokeredcertificatesofdeposit	12259000	USD
CY2020Q4	colb	Brokered Money Market Accounts BrokeredMoneyMarketAccounts	577804000	USD
CY2019Q4	colb	Brokered Money Market Accounts BrokeredMoneyMarketAccounts	300158000	USD
CY2020Q4	colb	Deposits Before Valuation Adjustment DepositsBeforeValuationAdjustment	13869862000	USD
CY2019Q4	colb	Deposits Before Valuation Adjustment DepositsBeforeValuationAdjustment	10684721000	USD
CY2020Q4	colb	Deposits Valuation Adjustment From Acquisition Accounting DepositsValuationAdjustmentFromAcquisitionAccounting	0	USD
CY2019Q4	colb	Deposits Valuation Adjustment From Acquisition Accounting DepositsValuationAdjustmentFromAcquisitionAccounting	-13000	USD
CY2020Q4	us-gaap	Deposits Deposits	13869862000	USD
CY2019Q4	us-gaap	Deposits Deposits	10684708000	USD
CY2020Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	1200000	USD
CY2019Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	3800000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	263037000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	51585000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	10185000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	8180000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	5809000	USD
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	49000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	338845000	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances General Debt Obligations Disclosures Maximum Amount Available FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresMaximumAmountAvailable	2090000000.00	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances General Debt Obligations Disclosures Maximum Amount Available FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresMaximumAmountAvailable	1960000000	USD
CY2020Q4	colb	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate Before Valuation Adjustment FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRateBeforeValuationAdjustment	7000000.0	USD
CY2019Q4	colb	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate Before Valuation Adjustment FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRateBeforeValuationAdjustment	953000000.0	USD
CY2020Q4	colb	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate One To Five Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateOneToFiveYearsFromBalanceSheetDate	0.0385
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate One To Five Years FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRateOneToFiveYears	2000000	USD
CY2020Q4	colb	Federal Home Loan Bank Advances Maturities Summary Average Interest Rate After Ten Years From Balance Sheet Date FederalHomeLoanBankAdvancesMaturitiesSummaryAverageInterestRateAfterTenYearsFromBalanceSheetDate	0.0537
CY2020Q4	colb	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate After Ten Years FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRateAfterTenYears	5000000	USD
CY2020Q4	colb	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate Before Valuation Adjustment FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRateBeforeValuationAdjustment	7000000	USD
CY2020Q4	colb	Federal Home Loan Bank Fixed Rate Advances Valuation Adjustment From Acquisition Accounting FederalHomeLoanBankFixedRateAdvancesValuationAdjustmentFromAcquisitionAccounting	414000	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Maturities Summary By Interest Rate Type Fixed Rate FederalHomeLoanBankAdvancesMaturitiesSummaryByInterestRateTypeFixedRate	7414000	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	7414000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	953469000	USD
CY2018Q4	us-gaap	Federal Home Loan Bank Advances Long Term FederalHomeLoanBankAdvancesLongTerm	399523000	USD
CY2020	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Balance Of Agreements Outstanding FederalHomeLoanBankAdvancesActivityForYearAverageBalanceOfAgreementsOutstanding	341643000	USD
CY2019	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Balance Of Agreements Outstanding FederalHomeLoanBankAdvancesActivityForYearAverageBalanceOfAgreementsOutstanding	469983000	USD
CY2018	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Balance Of Agreements Outstanding FederalHomeLoanBankAdvancesActivityForYearAverageBalanceOfAgreementsOutstanding	166563000	USD
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Activity For Year Maximum Outstanding At Any Month End FederalHomeLoanBankAdvancesActivityForYearMaximumOutstandingAtAnyMonthEnd	1005464000	USD
CY2019Q4	us-gaap	Federal Home Loan Bank Advances Activity For Year Maximum Outstanding At Any Month End FederalHomeLoanBankAdvancesActivityForYearMaximumOutstandingAtAnyMonthEnd	953469000	USD
CY2018Q4	us-gaap	Federal Home Loan Bank Advances Activity For Year Maximum Outstanding At Any Month End FederalHomeLoanBankAdvancesActivityForYearMaximumOutstandingAtAnyMonthEnd	399523000	USD
CY2020	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Interest Rate For Year FederalHomeLoanBankAdvancesActivityForYearAverageInterestRateForYear	0.0182
CY2019	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Interest Rate For Year FederalHomeLoanBankAdvancesActivityForYearAverageInterestRateForYear	0.0242
CY2018	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Interest Rate For Year FederalHomeLoanBankAdvancesActivityForYearAverageInterestRateForYear	0.0229
CY2020Q4	us-gaap	Federal Home Loan Bank Advances Activity For Year Average Interest Rate At Period End FederalHomeLoanBankAdvancesActivityForYearAverageInterestRateAtPeriodEnd	0.0494
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CY2018	colb	Federal Reserve Bank Advances Activityfortheyearaveragebalanceofagreementsoutstanding FederalReserveBankAdvancesActivityfortheyearaveragebalanceofagreementsoutstanding	14000	USD
CY2020Q4	colb	Federal Reserve Bank Advances Maximum Amount Available FederalReserveBankAdvancesMaximumAmountAvailable	234400000	USD
CY2019Q4	colb	Federal Reserve Bank Advances Maximum Amount Available FederalReserveBankAdvancesMaximumAmountAvailable	209100000	USD
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CY2020Q4	us-gaap	Line Of Credit Facility Maximum Borrowing Capacity LineOfCreditFacilityMaximumBorrowingCapacity	15000000.0	USD
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CY2019Q4	colb	Repurchaseagreementsamountsoffsetinbalancesheet Repurchaseagreementsamountsoffsetinbalancesheet	0	USD
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CY2019Q4	us-gaap	Securities Sold Under Agreements To Repurchase Collateral Right To Reclaim Securities SecuritiesSoldUnderAgreementsToRepurchaseCollateralRightToReclaimSecurities	64437000	USD
CY2019Q4	colb	Securitiessoldunderagreementstorepurchaseamountnotoffset Securitiessoldunderagreementstorepurchaseamountnotoffset	0	USD
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CY2020	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	79297	shares
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2200000	USD
CY2019	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	57201	shares
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2100000	USD
CY2018	us-gaap	Stock Issued During Period Shares Employee Stock Purchase Plans StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans	50750	shares
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	2000000.0	USD
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CY2019	us-gaap	Defined Benefit Plan Actuarial Gain Loss DefinedBenefitPlanActuarialGainLoss	2663000	USD
CY2020	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1887000	USD
CY2019	us-gaap	Defined Benefit Plan Net Periodic Benefit Cost DefinedBenefitPlanNetPeriodicBenefitCost	1930000	USD
CY2020	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	2235000	USD
CY2019	us-gaap	Defined Benefit Plan Benefit Obligation Benefits Paid DefinedBenefitPlanBenefitObligationBenefitsPaid	966000	USD
CY2020Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	27402000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Benefit Obligation DefinedBenefitPlanBenefitObligation	24914000	USD
CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	40367000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	148190000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	6362000	USD
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CY2020Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	182195000	USD
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CY2020Q4	us-gaap	Stock Repurchase Program Number Of Shares Authorized To Be Repurchased StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased	3500000	shares
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CY2019Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	40367000	USD
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CY2018Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-35305000	USD
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CY2019Q4	us-gaap	Equity Securities Without Readily Determinable Fair Value Amount EquitySecuritiesWithoutReadilyDeterminableFairValueAmount	0	USD
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CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	71999000	shares
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CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72032000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	72390000	shares
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CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	10700000	USD
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CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	44094000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	40471000	USD
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CY2019Q4	colb	Deferredtaxliabilitiespurchaseaccounting Deferredtaxliabilitiespurchaseaccounting	8946000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	2427000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Property Plant And Equipment DeferredTaxLiabilitiesPropertyPlantAndEquipment	3152000	USD
CY2020Q4	colb	Oregonstateoperatinglosscarryforwardssettobegintoexpirein2024 Oregonstateoperatinglosscarryforwardssettobegintoexpirein2024	85000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	7591000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Derivatives DeferredTaxLiabilitiesDerivatives	3452000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	112000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	100000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	98215000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	51930000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities DeferredTaxLiabilities	27529000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	923000	USD
CY2020	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	40402000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2019	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	50738000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2018	us-gaap	Income Tax Reconciliation Income Tax Expense Benefit At Federal Statutory Income Tax Rate IncomeTaxReconciliationIncomeTaxExpenseBenefitAtFederalStatutoryIncomeTaxRate	44485000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.21
CY2020	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	5987000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.03
CY2019	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	6771000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.03
CY2018	us-gaap	Income Tax Reconciliation Tax Exempt Income IncomeTaxReconciliationTaxExemptIncome	6423000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Tax Exempt Income EffectiveIncomeTaxRateReconciliationTaxExemptIncome	-0.03
CY2020	colb	Income Tax Reconciliation Life Insurance Proceeds IncomeTaxReconciliationLifeInsuranceProceeds	1348000	USD
CY2020	colb	Effective Income Tax Rate Reconciliation Life Insurance Proceeds EffectiveIncomeTaxRateReconciliationLifeInsuranceProceeds	-0.01
CY2019	colb	Income Tax Reconciliation Life Insurance Proceeds IncomeTaxReconciliationLifeInsuranceProceeds	1963000	USD
CY2019	colb	Effective Income Tax Rate Reconciliation Life Insurance Proceeds EffectiveIncomeTaxRateReconciliationLifeInsuranceProceeds	-0.01
CY2018	colb	Income Tax Reconciliation Life Insurance Proceeds IncomeTaxReconciliationLifeInsuranceProceeds	1261000	USD
CY2018	colb	Effective Income Tax Rate Reconciliation Life Insurance Proceeds EffectiveIncomeTaxRateReconciliationLifeInsuranceProceeds	-0.01
CY2020	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	4844000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.03
CY2019	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	5134000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.02
CY2018	us-gaap	Income Tax Reconciliation State And Local Income Taxes IncomeTaxReconciliationStateAndLocalIncomeTaxes	4931000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.02
CY2020	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	237000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0
CY2019	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	22000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0.01
CY2018	us-gaap	Income Tax Reconciliation Other Adjustments IncomeTaxReconciliationOtherAdjustments	-2778000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.01
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38148000	USD
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.20
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	47160000	USD
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.20
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38954000	USD
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.18
CY2020Q4	us-gaap	Deferred Tax Liability Not Recognized Amount Of Unrecognized Deferred Tax Liability Undistributed Earnings Of Domestic Subsidiaries DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfDomesticSubsidiaries	0	USD
CY2019Q4	us-gaap	Deferred Tax Liability Not Recognized Amount Of Unrecognized Deferred Tax Liability Undistributed Earnings Of Domestic Subsidiaries DeferredTaxLiabilityNotRecognizedAmountOfUnrecognizedDeferredTaxLiabilityUndistributedEarningsOfDomesticSubsidiaries	0	USD
CY2020	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0	USD
CY2019	us-gaap	Unrecognized Tax Benefits Income Tax Penalties And Interest Expense UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense	0	USD
CY2020Q4	colb	Federaloperatinglosscarryforwardssettobegintoexpirein2024 Federaloperatinglosscarryforwardssettobegintoexpirein2024	12700000	USD
CY2020Q4	colb	Idahostateoperatinglosscarryforwardssettobegintoexpirein2024 Idahostateoperatinglosscarryforwardssettobegintoexpirein2024	11500000	USD
CY2020Q4	colb	Capital Conservation Buffer CapitalConservationBuffer	0.0645
CY2020Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	1390958000	USD
CY2020Q4	colb	Common Equity Tier1 Capitalto Risk Weighted Assets CommonEquityTier1CapitaltoRiskWeightedAssets	0.1288
CY2020Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	486080000	USD
CY2020Q4	colb	Common Equity Tier1 Risk Based Capital Requiredfor Capital Adequacyto Risk Weighted Assets CommonEquityTier1RiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.0450
CY2020Q4	colb	Common Equity Tier One Capital Requiredfor Capital Adequacyminimumrequiredplusfullyphasedincapitalconservationbuffer CommonEquityTierOneCapitalRequiredforCapitalAdequacyminimumrequiredplusfullyphasedincapitalconservationbuffer	756125000	USD
CY2020Q4	colb	Common Equity Tier1 Risk Based Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin CommonEquityTier1RiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.0700
CY2020Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	1390958000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1288
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	648107000	USD
CY2020Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2020Q4	colb	Tier One Risk Based Capital Requiredfor Capital Adequacypluscapitalconservationbufferfullyphasedin TierOneRiskBasedCapitalRequiredforCapitalAdequacypluscapitalconservationbufferfullyphasedin	918152000	USD
CY2020Q4	colb	Tier One Based Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin TierOneBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.0850
CY2020Q4	us-gaap	Capital Capital	1561020000	USD
CY2020Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1445
CY2020Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	864143000	USD
CY2020Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2020Q4	colb	Capital Requiredfor Capital Adequacypluscapitalconservationbufferfullyphasedin CapitalRequiredforCapitalAdequacypluscapitalconservationbufferfullyphasedin	1134187000	USD
CY2020Q4	colb	Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin CapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.1050
CY2020Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	1390958000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.0886
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	628112000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	628112000	USD
CY2020Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2019Q4	us-gaap	Common Equity Tier One Capital CommonEquityTierOneCapital	1317202000	USD
CY2019Q4	colb	Common Equity Tier1 Capitalto Risk Weighted Assets CommonEquityTier1CapitaltoRiskWeightedAssets	0.1245
CY2019Q4	us-gaap	Common Equity Tier One Capital Required For Capital Adequacy CommonEquityTierOneCapitalRequiredForCapitalAdequacy	476260000	USD
CY2019Q4	colb	Common Equity Tier1 Risk Based Capital Requiredfor Capital Adequacyto Risk Weighted Assets CommonEquityTier1RiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssets	0.0450
CY2019Q4	colb	Common Equity Tier One Capital Requiredfor Capital Adequacyminimumrequiredplusfullyphasedincapitalconservationbuffer CommonEquityTierOneCapitalRequiredforCapitalAdequacyminimumrequiredplusfullyphasedincapitalconservationbuffer	740849000	USD
CY2019Q4	colb	Common Equity Tier1 Risk Based Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin CommonEquityTier1RiskBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.0700
CY2019Q4	us-gaap	Tier One Risk Based Capital TierOneRiskBasedCapital	1317202000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital To Risk Weighted Assets TierOneRiskBasedCapitalToRiskWeightedAssets	0.1245
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy TierOneRiskBasedCapitalRequiredForCapitalAdequacy	635014000	USD
CY2019Q4	us-gaap	Tier One Risk Based Capital Required For Capital Adequacy To Risk Weighted Assets TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0600
CY2019Q4	colb	Tier One Risk Based Capital Requiredfor Capital Adequacypluscapitalconservationbufferfullyphasedin TierOneRiskBasedCapitalRequiredforCapitalAdequacypluscapitalconservationbufferfullyphasedin	899603000	USD
CY2019Q4	colb	Tier One Based Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin TierOneBasedCapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.0850
CY2019Q4	us-gaap	Capital Capital	1439877000	USD
CY2019Q4	us-gaap	Capital To Risk Weighted Assets CapitalToRiskWeightedAssets	0.1360
CY2019Q4	us-gaap	Capital Required For Capital Adequacy CapitalRequiredForCapitalAdequacy	846685000	USD
CY2019Q4	us-gaap	Capital Required For Capital Adequacy To Risk Weighted Assets CapitalRequiredForCapitalAdequacyToRiskWeightedAssets	0.0800
CY2019Q4	colb	Capital Requiredfor Capital Adequacypluscapitalconservationbufferfullyphasedin CapitalRequiredforCapitalAdequacypluscapitalconservationbufferfullyphasedin	1111274000	USD
CY2019Q4	colb	Capital Requiredfor Capital Adequacyto Risk Weighted Assetspluscapitalconservationbufferfullyphasedin CapitalRequiredforCapitalAdequacytoRiskWeightedAssetspluscapitalconservationbufferfullyphasedin	0.1050
CY2019Q4	us-gaap	Tier One Leverage Capital TierOneLeverageCapital	1317202000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital To Average Assets TierOneLeverageCapitalToAverageAssets	0.1017
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	517938000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy TierOneLeverageCapitalRequiredForCapitalAdequacy	517938000	USD
CY2019Q4	us-gaap	Tier One Leverage Capital Required For Capital Adequacy To Average Assets TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets	0.0400
CY2020Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	133296000	USD
CY2020Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	127384000	USD
CY2020Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	126232000	USD
CY2020Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	130897000	USD
CY2020	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	517809000	USD
CY2020Q4	us-gaap	Interest Expense InterestExpense	2184000	USD
CY2020Q3	us-gaap	Interest Expense InterestExpense	2658000	USD
CY2020Q2	us-gaap	Interest Expense InterestExpense	4381000	USD
CY2020Q1	us-gaap	Interest Expense InterestExpense	8475000	USD
CY2020	us-gaap	Interest Expense InterestExpense	17698000	USD
CY2020Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	131112000	USD
CY2020Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	124726000	USD
CY2020Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	121851000	USD
CY2020Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	122422000	USD
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	500111000	USD
CY2020Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	-4700000	USD
CY2020Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	7400000	USD
CY2020Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	33500000	USD
CY2020Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	41500000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	77700000	USD
CY2020Q4	us-gaap	Noninterest Income NoninterestIncome	23562000	USD
CY2020Q3	us-gaap	Noninterest Income NoninterestIncome	22472000	USD
CY2020Q2	us-gaap	Noninterest Income NoninterestIncome	37259000	USD
CY2020Q1	us-gaap	Noninterest Income NoninterestIncome	21207000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	104500000	USD
CY2020Q4	us-gaap	Noninterest Expense NoninterestExpense	84300000	USD
CY2020Q3	us-gaap	Noninterest Expense NoninterestExpense	85115000	USD
CY2020Q2	us-gaap	Noninterest Expense NoninterestExpense	80833000	USD
CY2020Q1	us-gaap	Noninterest Expense NoninterestExpense	84271000	USD
CY2020	us-gaap	Noninterest Expense NoninterestExpense	334519000	USD
CY2020Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	75074000	USD
CY2020Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	54683000	USD
CY2020Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	44777000	USD
CY2020Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	17858000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	192392000	USD
CY2020Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16774000	USD
CY2020Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	9949000	USD
CY2020Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	8195000	USD
CY2020Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	3230000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	38148000	USD
CY2020Q4	us-gaap	Net Income Loss NetIncomeLoss	58300000	USD
CY2020Q3	us-gaap	Net Income Loss NetIncomeLoss	44734000	USD
CY2020Q2	us-gaap	Net Income Loss NetIncomeLoss	36582000	USD
CY2020Q1	us-gaap	Net Income Loss NetIncomeLoss	14628000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	154244000	USD
CY2020Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.82
CY2020Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.63
CY2020Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.52
CY2020Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.20
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.17
CY2020Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.82
CY2020Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.63
CY2020Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.52
CY2020Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.20
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.17
CY2019Q4	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	133109000	USD
CY2019Q3	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	132533000	USD
CY2019Q2	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	135422000	USD
CY2019Q1	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	128888000	USD
CY2019	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	529952000	USD
CY2019Q4	us-gaap	Interest Expense InterestExpense	8292000	USD
CY2019Q3	us-gaap	Interest Expense InterestExpense	10083000	USD
CY2019Q2	us-gaap	Interest Expense InterestExpense	10306000	USD
CY2019Q1	us-gaap	Interest Expense InterestExpense	7866000	USD
CY2019	us-gaap	Interest Expense InterestExpense	36547000	USD
CY2019Q4	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	124817000	USD
CY2019Q3	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	122450000	USD
CY2019Q2	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	125116000	USD
CY2019Q1	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	121022000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	493405000	USD
CY2019Q4	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1614000	USD
CY2019Q3	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	299000	USD
CY2019Q2	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	218000	USD
CY2019Q1	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	1362000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	3493000	USD
CY2019Q4	us-gaap	Noninterest Income NoninterestIncome	21807000	USD
CY2019Q3	us-gaap	Noninterest Income NoninterestIncome	28030000	USD
CY2019Q2	us-gaap	Noninterest Income NoninterestIncome	25648000	USD
CY2019Q1	us-gaap	Noninterest Income NoninterestIncome	21696000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	97181000	USD
CY2019Q4	us-gaap	Noninterest Expense NoninterestExpense	86978000	USD
CY2019Q3	us-gaap	Noninterest Expense NoninterestExpense	87076000	USD
CY2019Q2	us-gaap	Noninterest Expense NoninterestExpense	86728000	USD
CY2019Q1	us-gaap	Noninterest Expense NoninterestExpense	84700000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	345482000	USD
CY2019Q4	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	58032000	USD
CY2019Q3	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	63105000	USD
CY2019Q2	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	63818000	USD
CY2019Q1	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	56656000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	241611000	USD
CY2019Q4	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11903000	USD
CY2019Q3	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12378000	USD
CY2019Q2	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	12094000	USD
CY2019Q1	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10785000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	47160000	USD
CY2019Q4	us-gaap	Net Income Loss NetIncomeLoss	46129000	USD
CY2019Q3	us-gaap	Net Income Loss NetIncomeLoss	50727000	USD
CY2019Q2	us-gaap	Net Income Loss NetIncomeLoss	51724000	USD
CY2019Q1	us-gaap	Net Income Loss NetIncomeLoss	45871000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	194451000	USD
CY2019Q4	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.64
CY2019Q3	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.70
CY2019Q2	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.71
CY2019Q1	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	0.63
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.68
CY2019Q4	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.64
CY2019Q3	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.70
CY2019Q2	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.71
CY2019Q1	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	0.63
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.68
CY2020	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	27019000	USD
CY2019	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	35695000	USD
CY2018	colb	Depositaccountandtreasurymanagementfees Depositaccountandtreasurymanagementfees	36072000	USD
CY2020	colb	Cardrevenue Cardrevenue	13928000	USD
CY2019	colb	Cardrevenue Cardrevenue	15198000	USD
CY2018	colb	Cardrevenue Cardrevenue	19719000	USD
CY2020	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	12830000	USD
CY2019	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	12799000	USD
CY2018	colb	Financialservicesandtrustrevenue Financialservicesandtrustrevenue	12135000	USD
CY2020	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	53777000	USD
CY2019	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	63692000	USD
CY2018	colb	Revenuefromcontractswithcustomers Revenuefromcontractswithcustomers	67926000	USD
CY2020	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	50723000	USD
CY2019	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	33489000	USD
CY2018	colb	Noninterestincomeexcludingrevenuefromcontractswithcustomers Noninterestincomeexcludingrevenuefromcontractswithcustomers	20330000	USD
CY2020	us-gaap	Noninterest Income NoninterestIncome	104500000	USD
CY2019	us-gaap	Noninterest Income NoninterestIncome	97181000	USD
CY2018	us-gaap	Noninterest Income NoninterestIncome	88256000	USD

Files In Submission

Name	View Source	Status
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$COLB
Columbia Banking System Inc Stock $colb

2020 Q4 Form 10-K Financial Statement

#000088734321000065 Filed on February 26, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$COLB Columbia Banking System Inc Stock $colb

2020 Q4 Form 10-K Financial Statement

#000088734321000065 Filed on February 26, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$COLB
Columbia Banking System Inc Stock $colb