Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	COLUMBIA FUNDS SERIES TRUST I
Prospectus Date	rr_ProspectusDate	Mar. 01, 2015
Columbia Global Technology Growth Fund
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 Global Technology Growth Fund (the Fund) seeks capital appreciation by investing, under normal market conditions, at least 80% of its total net assets (plus any borrowings for investment purposes) in stocks of technology companies that may benefit from technological improvements, advancements or developments.
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 and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
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 68% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	68.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Other expenses are based on estimated amounts for the Fund’s current fiscal year.
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. 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 at least 80% of net assets (including the amount of any borrowings for investment purposes) in equity securities (including, but not limited to, common stocks, preferred stocks and securities convertible into common or preferred stocks) of technology companies that may benefit from technological improvements, advancements or developments. For these purposes, technology companies are those companies that, in the opinion of the Fund’s investment manager, use technology extensively to improve their business processes, applications and opportunities or seek to grow through technological developments and innovations.  Technology companies include companies in technology-related industries or sectors, such as the information technology, communications, healthcare, media, consumer electronics, semi-conductor, internet commerce and advertising, environmental, aerospace and defense industries and sectors. The Fund may invest in companies that have market capitalizations of any size and may invest a significant amount of its assets in smaller companies. Under normal circumstances, the Fund generally invests at least 40% of its net assets in foreign currencies, companies that maintain their principal place of business or conduct their principal business activities outside the U.S., companies that have their securities traded on non-U.S. exchanges or companies that have been formed under the laws of non-U.S. countries. The Fund considers a company to conduct its principal business activities outside the U.S. if it derives at least 50% of its revenue or profits from business outside the U.S. or has at least 50% of its sales or assets outside the U.S. From time to time, the Fund may be below this 40% level and, in such circumstances, the Fund will endeavor to invest its assets to bring the Fund’s net assets above this 40% level while giving due regard to the Investment Manager’s view of market and other conditions and available investment opportunities. Under normal circumstances, the Fund invests at least 25% of the value of its total net assets at the time of purchase in the securities of issuers conducting their principal business activities in the technology and related group of industries. The Fund invests primarily in common stocks of companies that the investment manager believes have the potential for long-term growth. The Fund’s investment strategy may involve the frequent trading of portfolio securities. The Fund may invest directly in foreign securities or indirectly through depositary receipts. The Fund is non-diversified, which means that it can invest a greater percentage of its assets in the securities of fewer issuers than can a diversified fund.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund involves risk, including those described below. There is no assurance that the Fund will achieve its investment objective and you may lose money. The value of the Fund’s holdings may decline, and the Fund’s net asset value (NAV) and share price may go down. Active Management Risk. Due to its active management, the Fund could underperform its benchmark index and/or other funds with similar investment objectives. Convertible Securities Risk. Convertible securities are subject to the usual risks associated with debt securities, such as interest rate risk and credit risk. Convertible securities also react to changes in the value of the common stock into which they convert, and are thus subject to market risk. The Fund may also be forced to convert a convertible security at an inopportune time, which may decrease the Fund’s return. Depositary Receipts Risk. Depositary receipts are receipts issued by a bank or trust company reflecting ownership of underlying securities issued by foreign companies. Some foreign securities are traded in the form of American Depositary Receipts (ADRs). Depositary receipts involve risks similar to the risks associated with investments in foreign securities, including those of the particular country, which may be related to the particular political, regulatory, economic, social and other conditions or events occurring in the country and fluctuations in its currency, as well as market risk tied to the underlying foreign company. In addition, ADR holders may have limited voting rights and may not have the same rights afforded typical company stockholders in the event of a corporate action such as an acquisition, merger or rights offering and may experience difficulty in receiving company stockholder communications. Foreign Securities Risk. Investments in or exposure to foreign securities involve certain risks not associated with investments in or exposure to securities of U.S. companies. Foreign securities subject the Fund to the risks associated with investing in the particular country of an issuer, including the political, regulatory, economic, social, diplomatic and other conditions or events 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. The performance of the Fund may be negatively impacted by fluctuations in a foreign currency’s strength or weakness relative to the U.S. dollar, particularly if the Fund invests a significant percentage of its assets in foreign securities or other assets denominated in currencies other than the U.S. dollar. Frequent Trading Risk. The portfolio managers may actively and frequently trade investments in the Fund's portfolio to carry out its investment strategies. Frequent trading of investments increases the possibility that the Fund, as relevant, will realize taxable capital gains (including short-term capital gains, which are generally taxable to shareholders at higher rates than long-term capital gains for U.S. federal income tax purposes), which could reduce the Fund's after-tax return. Frequent trading can also mean higher brokerage and other transaction costs, which could reduce the Fund's return. The trading costs and tax effects associated with portfolio turnover may adversely affect the Fund’s performance. 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. Issuer Risk. An issuer in which the Fund invests or to which it has exposure may perform poorly, and the value of its securities may therefore decline, which would negatively affect the Fund’s performance. Poor performance 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 or other events, conditions or factors. Market Risk. Market risk refers to the possibility that the market values of securities or other investments that the Fund holds will fall, sometimes rapidly or unpredictably, or fail to rise. An investment in the Fund could lose money over short or long periods. Although equity securities generally tend to have greater price volatility than debt securities, under certain market conditions, debt securities may have comparable or greater price volatility. Non-Diversified Fund Risk. The Fund is non-diversified, which generally means that it will invest a greater percentage of its total assets in the securities of fewer issuers than a “diversified” fund. This increases the risk that a change in the value of any one investment held by the Fund could affect the overall value of the Fund more than it would affect that of a diversified fund holding a greater number of investments. Accordingly, the Fund's value will likely be more volatile than the value of a more diversified fund. Sector Risk. At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a related group of industries within an economic sector, including the information technology and technology-related sectors. Companies in the same economic sector may be similarly affected by economic, regulatory, political or market events or conditions, which may make the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly. The more broadly a Fund invests, the more it spreads risk and potentially reduces the risks of loss and volatility. The Fund may be more susceptible to the particular risks that may affect companies in the information technology sector, as well as other technology-related sectors (collectively, the technology sectors) than if it were invested in a wider variety of companies in unrelated sectors. Companies in the technology sectors 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 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. Small Company Securities Risk. Investments in small-capitalization companies (small-cap companies) often involve greater risks than investments in larger, more established companies (larger companies) because small-cap companies tend to have less predictable earnings and may lack the management experience, financial resources, product diversification and competitive strengths of larger companies, and securities of small-cap companies may be less liquid and more volatile than the securities of larger companies.
Risk Lose Money [Text]	rr_RiskLoseMoney	There is no assurance that the Fund will achieve its investment objective and you may lose money.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversified Fund Risk. The Fund is non-diversified, which generally means that it will invest a greater percentage of its total assets in the securities of fewer issuers than a “diversified” fund. This increases the risk that a change in the value of any one investment held by the Fund could affect the overall value of the Fund more than it would affect that of a diversified fund holding a greater number of investments. Accordingly, the Fund's value will likely be more volatile than the value of a more diversified fund.
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 A share performance (without sales charges) has varied for each full calendar year shown. If the sales charges were reflected, returns shown would be lower. Class A and Class Z shares are offered in a separate prospectus. The table below the bar chart compares the Fund’s returns (after applicable sales charges shown in the Shareholder Fees table in this prospectus) for the periods shown with a broad measure of market performance. Class I shares of the Fund did not commence operations prior to the date of this prospectus and, therefore, performance is not yet available. Any share class that does not have available performance would have annual returns substantially similar to those of Class Z shares. Except for differences in annual returns resulting from differences in expenses and sales charges (where applicable), the 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 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-deferred accounts such as 401(k) plans or Individual Retirement Accounts (IRAs). The after-tax returns are shown only for Class A 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 columbiamanagement.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 A share performance (without sales charges) has varied for each full calendar year shown. If the sales charges were reflected, returns shown would be lower. Class A and Class Z shares are offered in a separate prospectus. The table below the bar chart compares the Fund’s returns (after applicable sales charges shown in the Shareholder Fees table in this prospectus) for the periods shown with a broad measure of market performance.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Class I shares of the Fund did not commence operations prior to the date of this prospectus and, therefore, performance is not yet available.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	800.345.6611
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	columbiamanagement.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 Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The bar chart shows how the Fund’s Class A share performance (without sales charges) has varied for each full calendar year shown. If the sales charges were reflected, returns shown would be lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best and Worst Quarterly Returns During the Period Shown in the Bar Chart Best                            1st Quarter 2012                            23.37% Worst                         4th Quarter 2008                           -28.61%
Bar Chart, Returns for Class Not Offered in Prospectus [Text]	rr_BarChartReturnsForClassNotOfferedInProspectus	The bar chart shows how the Fund’s Class A share performance (without sales charges) has varied for each full calendar year shown. If the sales charges were reflected, returns shown would be lower. Class A and Class Z shares are offered in a separate prospectus. Class I shares of the Fund did not commence operations prior to the date of this prospectus and, therefore, performance is not yet available. Any share class that does not have available performance would have annual returns substantially similar to those of Class Z shares.
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns After Applicable Sales Charges (for periods ended December 31, 2014)
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 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-deferred 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 A shares and will vary for other share classes.
Columbia Global Technology Growth Fund | Class I
Risk/Return:	rr_RiskReturnAbstract
Maximum sales charge (load) imposed on purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum deferred sales charge (load) imposed on redemptions	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.87%
Distribution and/or service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.11%	[1]
Total annual Fund operating expenses	rr_ExpensesOverAssets	0.98%
1 year	rr_ExpenseExampleYear01	100
3 years	rr_ExpenseExampleYear03	312
5 years	rr_ExpenseExampleYear05	542
10 years	rr_ExpenseExampleYear10	1,201
1 year	rr_ExpenseExampleNoRedemptionYear01	100
3 years	rr_ExpenseExampleNoRedemptionYear03	312
5 years	rr_ExpenseExampleNoRedemptionYear05	542
10 years	rr_ExpenseExampleNoRedemptionYear10	1,201
Columbia Global Technology Growth Fund | Class A
Risk/Return:	rr_RiskReturnAbstract
2005	rr_AnnualReturn2005	16.53%
2006	rr_AnnualReturn2006	8.71%
2007	rr_AnnualReturn2007	23.12%
2008	rr_AnnualReturn2008	(51.14%)
2009	rr_AnnualReturn2009	50.60%
2010	rr_AnnualReturn2010	25.57%
2011	rr_AnnualReturn2011	(14.79%)
2012	rr_AnnualReturn2012	18.22%
2013	rr_AnnualReturn2013	46.33%
2014	rr_AnnualReturn2014	16.66%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	23.37%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(28.61%)
1 Year	rr_AverageAnnualReturnYear01	9.98%
5 Years	rr_AverageAnnualReturnYear05	15.28%
10 Years	rr_AverageAnnualReturnYear10	8.85%
Share Class Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 01, 2002
Columbia Global Technology Growth Fund | returns after taxes on distributions | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.39%
5 Years	rr_AverageAnnualReturnYear05	14.94%
10 Years	rr_AverageAnnualReturnYear10	8.42%
Share Class Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 01, 2002
Columbia Global Technology Growth Fund | returns after taxes on distributions and sale of Fund shares | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.19%
5 Years	rr_AverageAnnualReturnYear05	12.24%
10 Years	rr_AverageAnnualReturnYear10	7.12%
Share Class Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 01, 2002
Columbia Global Technology Growth Fund | returns before taxes (without sales charges) | Class A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	16.66%
5 Years	rr_AverageAnnualReturnYear05	16.64%
10 Years	rr_AverageAnnualReturnYear10	9.50%
Share Class Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 01, 2002
Columbia Global Technology Growth Fund | Bank of America Merrill Lynch 100 Technology Index (reflects no deductions for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	10.73%
5 Years	rr_AverageAnnualReturnYear05	12.17%
10 Years	rr_AverageAnnualReturnYear10	7.11%

[1] Other expenses are based on estimated amounts for the Fund's current fiscal year.