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S000009184 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Summary of the Fund
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
Columbia Acorn® Fund (the Fund) seeks long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock
This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and members of your immediate family invest, or agree to invest in the future, at least $50,000 in certain classes of shares of eligible funds distributed by Columbia Management Investment Distributors, Inc. (the Distributor). More information is available about these and other sales charge discounts and waivers from your financial intermediary, and can be found in the Choosing a Share Class section beginning on page 21 of the Fund’s prospectus, in Appendix A to the prospectus beginning on page A-1 and in Appendix S to the Statement of Additional Information (SAI) under Sales Charge Waivers beginning on page S-1. 
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses(c) (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination April 30, 2027
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock
The Fund may pay transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 81% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 81.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and members of your immediate family invest, or agree to invest in the future, at least $50,000 in certain classes of shares of eligible funds distributed by Columbia Management Investment Distributors, Inc. (the Distributor). More information is available about these and other sales charge discounts and waivers from your financial intermediary, and can be found in the Choosing a Share Class section beginning on page 21 of the Fund’s prospectus, in Appendix A to the prospectus beginning on page A-1 and in Appendix S to the Statement of Additional Information (SAI) under Sales Charge Waiversbeginning on page S-1.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expenses Restated to Reflect Current [Text] rr_ExpensesRestatedToReflectCurrent Expenses have been restated based on estimated amounts for the Fund's current fiscal year.
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees “Total annual Fund operating expenses” include acquired fund fees and expenses (expenses the Fund incurs indirectly through its investments in other investment companies) and may be higher than the ratio of expenses to average net assets shown in the Financial Highlights section of this prospectus because the ratio of expenses to average net assets does not include acquired fund fees and expenses.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock
The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:
■
you invest $10,000 in the applicable class of Fund shares for the periods indicated,
■
your investment has a 5% return each year, and
■
the Fund’s total annual operating expenses remain the same as shown in the Annual Fund Operating Expenses table above.
Class C shares’ 10-year cost examples below reflect the Class C shares' 8-year conversion policy. 
Since the waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire as indicated in the preceding table, they are only reflected in the 1 year example and the first two years of the other examples. Although your actual costs may be higher or lower, based on the assumptions listed above, your costs would be: 
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations generally in the range of market capitalizations in the Russell 2500® Growth Index (the Index) at the time of purchase (between $5.2 million and $31.9 billion as of March 31, 2025). The market capitalization range and composition of companies in the Index are subject to change.
The Fund invests the majority of its assets in U.S. companies, but also may invest up to 33% of its total assets in foreign companies in developed markets (for example, Japan, Canada and the United Kingdom) and in emerging markets (for example, China, India and Brazil). The Fund may at times emphasize one or more sectors in selecting its investments, including the consumer discretionary, health care, industrials, and information technology sectors.
Risk [Heading] rr_RiskHeading Principal Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following bar chart and table show you how the Fund has performed in the past, and can help you understand the risks of investing in the Fund. The bar chart shows how the Fund’s Class Inst share performance has varied for each full calendar year shown. The table below the bar chart compares the Fund’s returns for the periods shown with a broad measure of market performance, as well as another measure of performance for markets in which the Fund may invest.
Effective August 1, 2024, the Fund compares its performance to the Russell 3000® Index, a broad-based performance index, as required by new regulatory requirements. The Fund’s performance also continues to be compared to its prior benchmark, which management believes more closely represents the market sectors and/or asset classes in which the Fund primarily invests.
The performance of one or more share classes shown in the table below begins before the indicated inception date for such share class. The returns shown for each such share class include the returns of the Fund’s Class Inst shares (adjusted to reflect the higher class-related operating expenses of such share classes, where applicable) for periods prior to its inception date. Share classes with expenses that are higher than Class Inst shares will have performance that is lower than Class Inst shares.
Except for differences in fees and expenses, all share classes of the Fund would have substantially similar annual returns because all share classes of the Fund invest in the same portfolio of securities.
The after-tax returns shown in the Average Annual Total Returns table below are calculated using the highest historical individual U.S. federal marginal income tax rates in effect during the period indicated in the table and do not reflect the impact of state, local or foreign taxes. Your actual after-tax returns will depend on your personal tax situation and may differ from those shown in the table. In addition, the after-tax returns shown in the table do not apply to shares held in tax-advantaged accounts such as 401(k) plans or Individual Retirement Accounts (IRAs). The after-tax returns are shown only for Class Inst shares and will vary for other share classes.
The Fund’s past performance (before and after taxes) is no guarantee of how the Fund will perform in the future. Updated performance information can be obtained by calling toll-free 800.345.6611 or visiting columbiathreadneedleus.com. 
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table show you how the Fund has performed in the past, and can help you understand the risks of investing in the Fund. The bar chart shows how the Fund’s Class Inst share performance has varied for each full calendar year shown. The table below the bar chart compares the Fund’s returns for the periods shown with a broad measure of market performance, as well as another measure of performance for markets in which the Fund may invest.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 800.345.6611
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress columbiathreadneedleus.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is no guarantee of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Year by Year Total Return (%)as of December 31 Each Year
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best and Worst Quarterly Returns During the Period Shown in the Bar Chart Best 2nd Quarter 2020 28.34% Worst 2nd Quarter 2022 -23.57%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns After Applicable Sales Charges (for periods ended December 31, 2024)
Performance Table Market Index Changed rr_PerformanceTableMarketIndexChanged Effective August 1, 2024, the Fund compares its performance to the Russell 3000® Index, a broad-based performance index, as required by new regulatory requirements. The Fund’s performance also continues to be compared to its prior benchmark, which management believes more closely represents the market sectors and/or asset classes in which the Fund primarily invests.
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate The after-tax returns shown in the Average Annual Total Returns table below are calculated using the highest historical individual U.S. federal marginal income tax rates in effect during the period indicated in the table and do not reflect the impact of state, local or foreign taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred In addition, the after-tax returns shown in the table do not apply to shares held in tax-advantaged accounts such as 401(k) plans or Individual Retirement Accounts (IRAs).
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Class Inst shares and will vary for other share classes.
S000009184 [Member] | Risk Lose Money [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock There is no assurance that the Fund will achieve its investment objective and you may lose money.
S000009184 [Member] | Risk Not Insured Depository Institution [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
S000009184 [Member] | Active Management Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Active Management Risk. Due to its active management, the Fund could underperform its benchmark index and/or other funds with similar investment objectives and/or strategies.
S000009184 [Member] | Foreign Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Foreign Securities Risk. Investments in or exposure to securities of foreign companies may involve heightened risks relative to investments in or exposure to securities of U.S. companies. Investing in securities of foreign companies subjects the Fund to the risks associated with an issuer’s (and any of its related companies’) country of organization and places of business operations, including risks related to political, regulatory, economic, social, diplomatic and other conditions or events (including, for example, military confrontations and actions, war, other conflicts, terrorism and disease/virus outbreaks and epidemics) occurring in the country or region, as well as risks associated with less developed custody and settlement practices. Foreign securities may be more volatile and less liquid than securities of U.S. companies, and are subject to the risks associated with potential imposition of economic and other sanctions against a particular foreign country, its nationals or industries or businesses within the country. In addition, foreign governments may impose withholding or other taxes on the Fund’s income, capital gains or proceeds from the disposition of foreign securities, which could reduce the Fund’s return on such securities.
S000009184 [Member] | Growth Securities Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Growth Securities Risk. Growth securities typically trade at a higher multiple of earnings than other types of equity securities. Accordingly, the market values of growth securities may never reach their expected market value and may decline in price. In addition, growth securities, at times, may not perform as well as value securities or the stock market in general, and may be out of favor with investors for varying periods of time. Growth securities may also be sensitive to movements in interest rates.
S000009184 [Member] | Issuer Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Issuer Risk. An issuer in which the Fund invests or to which it has exposure may perform poorly or below expectations, and the value of its securities may therefore decline, which may negatively affect the Fund’s performance. Underperformance of an issuer may be caused by poor management decisions, competitive pressures, breakthroughs in technology, reliance on suppliers, labor problems or shortages, corporate restructurings, fraudulent disclosures, natural disasters, military confrontations and actions, war, other conflicts, terrorism, disease/virus outbreaks, epidemics or other events, conditions and factors which may impair the value of your investment in the Fund.
■
Small- and Mid-Cap Stock Risk. Investments in small- and mid-capitalization companies (small- and mid-cap companies) often involve greater risks than investments in larger, more established companies (larger companies) because small- and mid-cap companies tend to have less predictable earnings and may lack the management experience, financial resources, product diversification and competitive strengths of larger companies. Securities of small- and mid-cap companies may be less liquid and more volatile than the securities of larger companies.
S000009184 [Member] | Market Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Market Risk. The Fund may incur losses due to declines in the value of one or more securities in which it invests. These declines may be due to factors affecting a particular issuer, or the result of, among other things, political, regulatory, market, economic or social developments affecting the relevant market(s) more generally. In addition, turbulence in financial markets and reduced liquidity in equity, credit and/or fixed income markets may negatively affect many issuers, which could adversely affect the Fund’s ability to price or value hard-to-value assets in thinly traded and closed markets and could cause significant redemptions and operational challenges. Global economies and financial markets are increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market. These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies worldwide. As a result, local, regional or global events such as terrorism, war, other conflicts, natural disasters, disease/virus outbreaks and epidemics or other public health issues, recessions, depressions or other events – or the potential for such events – could have a significant negative impact on global economic and market conditions.
S000009184 [Member] | Sector Risk [Member]  
Risk/Return: rr_RiskReturnAbstract  
Risk [Text Block] rr_RiskTextBlock
Sector Risk. At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in an industry or related group of industries within one or more economic sectors, including the consumer discretionary, health care, industrials, and information technology sectors. Companies in the same sector may be similarly affected by economic, regulatory, political or market events or conditions, which may make the Fund vulnerable to unfavorable developments in that industry, group of industries or economic sector.
■
Consumer Discretionary Sector. The Fund is vulnerable to the particular risks that may affect companies in the consumer discretionary sector. Companies in the consumer discretionary sector are subject to certain risks, including fluctuations in the performance of the overall domestic and international economies, interest rate changes, increased competition and consumer confidence. Performance of such companies may be affected by factors including reduced disposable household income, reduced consumer spending, and changing demographics and consumer tastes.
■
Health Care Sector. The Fund is vulnerable to the particular risks that may affect companies in the health care sector. Companies in the health care sector are subject to certain risks, including restrictions on government reimbursement for medical expenses, government approval of medical products and services, competitive pricing pressures, and the rising cost of medical products and services (especially for companies dependent upon a relatively limited number of products or services), among others. Performance of such companies may be affected by factors including government regulation, obtaining and protecting patents (or the failure to do so), product liability and other similar litigation as well as product obsolescence.
■
Industrials Sector. The Fund is vulnerable to the particular risks that may affect companies in the industrials sector. Companies in the industrials sector are subject to certain risks, including changes in supply and demand for their specific product or service and for industrial sector products in general, including decline in demand for such products due to rapid technological developments and frequent new product introduction. Performance of such companies may be affected by factors including government regulation, world events, economic conditions and risks for environmental damage and product liability claims.
■
Information Technology Sector. The Fund is vulnerable to the particular risks that may affect companies in the information technology sector. Companies in the information technology sector are subject to certain risks, including the risk that new services, equipment or technologies will not be accepted by consumers and businesses or will become rapidly obsolete. Performance of such companies may be affected by factors including obtaining and protecting patents (or the failure to do so) and significant competitive pressures, including aggressive pricing of their products or services, new market entrants, competition for market share and short product cycles due to an accelerated rate of technological developments. Such competitive pressures may lead to limited earnings and/or falling profit margins. As a result, the value of their securities may fall or fail to rise. In addition, many information technology sector companies have limited operating histories and prices of these companies’ securities historically have been more volatile than other securities, especially over the short term. Some companies in the information technology sector are facing increased government and regulatory scrutiny and may be subject to adverse government or regulatory action, which could negatively impact the value of their securities.
S000009184 [Member] | C000024954 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther 1.00% [1]
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25% [2]
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 1.10% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 1.07% [2]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock This charge is imposed on certain investments of between $1 million and $50 million redeemed within 18 months after purchase, as follows: 1.00% if redeemed within 12 months after purchase, and 0.50% if redeemed more than 12, but less than 18, months after purchase, with certain limited exceptions.
1 year rr_ExpenseExampleYear01 $ 678
3 years rr_ExpenseExampleYear03 899
5 years rr_ExpenseExampleYear05 1,141
10 years rr_ExpenseExampleYear10 1,833
1 year rr_ExpenseExampleNoRedemptionYear01 678
3 years rr_ExpenseExampleNoRedemptionYear03 899
5 years rr_ExpenseExampleNoRedemptionYear05 1,141
10 years rr_ExpenseExampleNoRedemptionYear10 $ 1,833
1 Year rr_AverageAnnualReturnYear01 7.55%
5 Years rr_AverageAnnualReturnYear05 3.95%
10 Years rr_AverageAnnualReturnYear10 6.95%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Oct. 16, 2000
S000009184 [Member] | C000024956 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther 1.00% [5]
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 1.00% [2]
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 1.85% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 1.82% [2]
Expenses Deferred Charges [Text Block] rr_ExpensesDeferredChargesTextBlock This charge applies to redemptions within 12 months after purchase, with certain limited exceptions.
1 year rr_ExpenseExampleYear01 $ 285
3 years rr_ExpenseExampleYear03 576
5 years rr_ExpenseExampleYear05 995
10 years rr_ExpenseExampleYear10 1,968
1 year rr_ExpenseExampleNoRedemptionYear01 185
3 years rr_ExpenseExampleNoRedemptionYear03 576
5 years rr_ExpenseExampleNoRedemptionYear05 995
10 years rr_ExpenseExampleNoRedemptionYear10 $ 1,968
1 Year rr_AverageAnnualReturnYear01 12.28%
5 Years rr_AverageAnnualReturnYear05 4.40%
10 Years rr_AverageAnnualReturnYear10 6.78%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Oct. 16, 2000
S000009184 [Member] | C000024957 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none [2]
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 0.85% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 0.82% [2]
1 year rr_ExpenseExampleYear01 $ 84
3 years rr_ExpenseExampleYear03 265
5 years rr_ExpenseExampleYear05 465
10 years rr_ExpenseExampleYear10 1,043
1 year rr_ExpenseExampleNoRedemptionYear01 84
3 years rr_ExpenseExampleNoRedemptionYear03 265
5 years rr_ExpenseExampleNoRedemptionYear05 465
10 years rr_ExpenseExampleNoRedemptionYear10 $ 1,043
2015 rr_AnnualReturn2015 (1.57%)
2016 rr_AnnualReturn2016 10.39%
2017 rr_AnnualReturn2017 25.24%
2018 rr_AnnualReturn2018 (5.09%)
2019 rr_AnnualReturn2019 26.60%
2020 rr_AnnualReturn2020 29.51%
2021 rr_AnnualReturn2021 8.99%
2022 rr_AnnualReturn2022 (33.78%)
2023 rr_AnnualReturn2023 21.85%
2024 rr_AnnualReturn2024 14.46%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 28.34%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.57%)
1 Year rr_AverageAnnualReturnYear01 14.46%
5 Years rr_AverageAnnualReturnYear05 5.45%
10 Years rr_AverageAnnualReturnYear10 7.86%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Jun. 10, 1970
S000009184 [Member] | C000122736 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none [2]
Other expenses rr_OtherExpensesOverAssets 0.09% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 0.81% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 0.78% [2]
1 year rr_ExpenseExampleYear01 $ 80
3 years rr_ExpenseExampleYear03 252
5 years rr_ExpenseExampleYear05 444
10 years rr_ExpenseExampleYear10 996
1 year rr_ExpenseExampleNoRedemptionYear01 80
3 years rr_ExpenseExampleNoRedemptionYear03 252
5 years rr_ExpenseExampleNoRedemptionYear05 444
10 years rr_ExpenseExampleNoRedemptionYear10 $ 996
1 Year rr_AverageAnnualReturnYear01 14.51%
5 Years rr_AverageAnnualReturnYear05 5.48%
10 Years rr_AverageAnnualReturnYear10 7.89%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Nov. 08, 2012
S000009184 [Member] | C000122737 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none [2]
Other expenses rr_OtherExpensesOverAssets 0.05% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 0.77% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 0.74% [2]
1 year rr_ExpenseExampleYear01 $ 76
3 years rr_ExpenseExampleYear03 240
5 years rr_ExpenseExampleYear05 422
10 years rr_ExpenseExampleYear10 948
1 year rr_ExpenseExampleNoRedemptionYear01 76
3 years rr_ExpenseExampleNoRedemptionYear03 240
5 years rr_ExpenseExampleNoRedemptionYear05 422
10 years rr_ExpenseExampleNoRedemptionYear10 $ 948
1 Year rr_AverageAnnualReturnYear01 14.50%
5 Years rr_AverageAnnualReturnYear05 5.51%
10 Years rr_AverageAnnualReturnYear10 7.94%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Nov. 08, 2012
S000009184 [Member] | C000251059 [Member]  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a % of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the original purchase price or current net asset value) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 0.72% [2]
Distribution and/or service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none [2]
Other expenses rr_OtherExpensesOverAssets 0.13% [2]
Total annual Fund operating expenses rr_ExpensesOverAssets 0.85% [2],[3]
Less: Fee waivers and/or expense reimbursements rr_FeeWaiverOrReimbursementOverAssets (0.03%) [2],[4]
Total annual Fund operating expenses after fee waivers and/or expense reimbursements rr_NetExpensesOverAssets 0.82% [2]
1 year rr_ExpenseExampleYear01 $ 84
3 years rr_ExpenseExampleYear03 265
5 years rr_ExpenseExampleYear05 465
10 years rr_ExpenseExampleYear10 1,043
1 year rr_ExpenseExampleNoRedemptionYear01 84
3 years rr_ExpenseExampleNoRedemptionYear03 265
5 years rr_ExpenseExampleNoRedemptionYear05 465
10 years rr_ExpenseExampleNoRedemptionYear10 $ 1,043
1 Year rr_AverageAnnualReturnYear01 14.46%
5 Years rr_AverageAnnualReturnYear05 5.45%
10 Years rr_AverageAnnualReturnYear10 7.86%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Oct. 02, 2024
S000009184 [Member] | returns after taxes on distributions | C000024957 [Member]  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 14.46%
5 Years rr_AverageAnnualReturnYear05 3.37%
10 Years rr_AverageAnnualReturnYear10 3.84%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Jun. 10, 1970
S000009184 [Member] | returns after taxes on distributions and sale of Fund shares | C000024957 [Member]  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 8.56%
5 Years rr_AverageAnnualReturnYear05 4.14%
10 Years rr_AverageAnnualReturnYear10 5.25%
Share Class Inception Date rr_AverageAnnualReturnInceptionDate Jun. 10, 1970
S000009184 [Member] | Russell 2500® Growth Index (reflects no deductions for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 13.90%
5 Years rr_AverageAnnualReturnYear05 8.08%
10 Years rr_AverageAnnualReturnYear10 9.45%
S000009184 [Member] | Russell 3000® Index (reflects no deductions for fees, expenses or taxes)  
Risk/Return: rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 23.81%
5 Years rr_AverageAnnualReturnYear05 13.86%
10 Years rr_AverageAnnualReturnYear10 12.55%
[1] This charge is imposed on certain investments of between $1 million and $50 million redeemed within 18 months after purchase, as follows: 1.00% if redeemed within 12 months after purchase, and 0.50% if redeemed more than 12, but less than 18, months after purchase, with certain limited exceptions.
[2] Expenses have been restated based on estimated amounts for the Fund's current fiscal year.
[3] “Total annual Fund operating expenses” include acquired fund fees and expenses (expenses the Fund incurs indirectly through its investments in other investment companies) and may be higher than the ratio of expenses to average net assets shown in the Financial Highlights section of this prospectus because the ratio of expenses to average net assets does not include acquired fund fees and expenses.
[4] Columbia Wanger Asset Management, LLC (the Investment Manager) and certain of its affiliates have contractually agreed to waive fees and/or to reimburse expenses (excluding transaction costs and certain other investment related expenses, interest, taxes, acquired fund fees and expenses, and infrequent and/or unusual expenses) through April 30, 2027, unless sooner terminated at the sole discretion of the Fund’s Board of Trustees. Under this agreement, the Fund’s net operating expenses, subject to applicable exclusions, will not exceed the annual rates of 1.07% for Class A, 1.82% for Class C, 0.82% for Class Inst, 0.78% for Class Inst2, 0.74% for Class Inst3 and 0.82% for Class S. Any difference in these annual rates relative to the annual rates noted in the last row of the above table (e.g., net expense ratios) are due to applicable exclusions under the agreement.
[5] This charge applies to redemptions within 12 months after purchase, with certain limited exceptions.