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Label Element Value
Risk Return Abstract rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Nov. 30, 2017
Registrant Name dei_EntityRegistrantName Investment Managers Series Trust
Central Index Key dei_EntityCentralIndexKey 0001318342
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Mar. 29, 2018
Document Effective Date dei_DocumentEffectiveDate Apr. 01, 2018
Prospectus Date rr_ProspectusDate Apr. 01, 2018
Riverbridge Growth Fund  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

SUMMARY SECTION - RIVERBRIDGE GROWTH FUND
Objective [Heading] rr_ObjectiveHeading

Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The investment objective of the Riverbridge Growth Fund (the "Growth Fund") is to seek 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 and hold shares of the Growth 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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination March 31, 2019
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Growth Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover 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 Growth Fund's performance. During the most recent fiscal year, the Growth Fund's portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The "Total annual fund operating expenses" and "Total annual fund operating expenses after waiving fees and/or reimbursing expenses" do not correlate to the ratio of expenses to average net assets appearing in the financial highlights table, which reflects only the operating expenses of the Growth Fund and does not include acquired fund fees and expenses.
Expense Example [Heading] rr_ExpenseExampleHeading

Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Growth Fund with the cost of investing in other mutual funds.

 

The example assumes that you invest $10,000 in the Growth Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Growth Fund's operating expenses remain the same.

 

Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal circumstances, the Growth Fund invests in equity securities of companies of any size, including small- and mid-capitalization companies. The Growth Fund's investments in equity securities may include common stock, preferred stock and convertible securities. While the Growth Fund invests primarily in equity securities of U.S. issuers, it may invest in securities of non-U.S. issuers. The Growth Fund's investments in foreign securities are primarily comprised of U.S. dollar-denominated securities of foreign issuers traded in the United States and American Depositary Receipts ("ADRs"). ADRs are receipts that represent interests in foreign securities held on deposit by U.S. banks. The Growth Fund will invest in a portfolio of securities typically spread across many economic sectors, although from time to time, the Fund may have a significant portion of its assets in one or more market sectors such as the information technology sector. In seeking to diversify the Growth Fund's portfolio, the Fund's advisor focuses on the portfolio's earnings catalysts rather than formal limitation of exposure to market sectors. The advisor seeks to limit the portfolio exposure of the Growth Fund to a common earnings catalyst (e.g., consumer spending) to no more than 20% of the Fund's net assets.

 

The Growth Fund's advisor, Riverbridge Partners, LLC (the "Advisor"), believes that earnings power determines the value of a franchise. The Advisor focuses on companies that it views as building their earnings power and building their intrinsic, or actual, values over long periods of time. The Advisor uses a bottom-up approach that seeks to identify high quality growth companies that demonstrate the ability to sustain strong secular earnings growth, regardless of overall economic conditions.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Growth Fund will invest in a portfolio of securities typically spread across many economic sectors, although from time to time, the Fund may have a significant portion of its assets in one or more market sectors such as the information technology sector.
Risk [Heading] rr_RiskHeading

Principal Risks of Investing
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Risk is inherent in all investing and you could lose money by investing in the Fund. A summary description of certain principal risks of investing in the Growth Fund is set forth below. Before you decide whether to invest in the Growth Fund, carefully consider these risk factors associated with investing in the Growth Fund, which may cause investors to lose money. There can be no assurance that the Growth Fund will achieve its investment objective.

 

Convertible securities risk. Convertible securities are subject to market and interest rate risk and credit risk. When the market price of the equity security underlying a convertible security decreases the convertible security tends to trade on the basis of its yield and other fixed income characteristics, and is more susceptible to credit and interest rate risks. When the market price of such equity security rises, the convertible security tends to trade on the basis of its equity conversion features and be more exposed to market risk. Convertible securities are typically issued by smaller capitalized companies with stock prices that may be more volatile than those of other companies.

 

Equity risk. The value of the equity securities held by the Growth Fund may fall due to general market and economic conditions, perceptions regarding the industries in which the issuers of securities held by the Growth Fund participate, or factors relating to specific companies in which the Growth Fund invests.

 

Foreign investment risk. The prices of foreign securities may be more volatile than the prices of securities of U.S. issuers because of economic and social conditions abroad, political developments, and changes in the regulatory environments of foreign countries. In addition, changes in exchange rates and interest rates may adversely affect the values of the Growth Fund's foreign investments. Foreign companies are generally subject to different legal and accounting standards than U.S. companies, and foreign financial intermediaries may be subject to less supervision and regulation than U.S. financial firms. Foreign securities include American Depository Receipts ("ADRs"). Unsponsored ADRs are organized independently and without the cooperation of the foreign issuer of the underlying securities, and involve additional risks because U.S. reporting requirements do not apply. In addition, the issuing bank may deduct shareholder distribution, custody, foreign currency exchange, and other fees from the payment of dividends.

 

Growth-oriented investment strategies risk. Growth funds generally focus on stocks of companies believed to have above-average potential for growth in revenue and earnings. Growth securities typically are very sensitive to market movements because their market prices frequently reflect projections of future earnings or revenues, and when it appears that those expectations will not be met, the prices of growth securities typically fall.

 

Management and strategy risk. The value of your investment depends on the judgment of the Advisor about the quality, relative yield, value or market trends affecting a particular security, industry, sector or region, which may prove to be incorrect.

 

Market risk. The market price of a security or instrument may decline, sometimes rapidly or unpredictably, due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic or political conditions throughout the world, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. The market value of a security or instrument also may decline because of factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry.

 

Preferred stock risk. Preferred stock represents an equity interest in a company that generally entitles the holder to receive, in preference to the holders of other stocks such as common stock, dividends and a fixed share of the proceeds resulting from a liquidation of the company. The market value of preferred stock is subject to company-specific and market risks applicable generally to equity securities and is also sensitive to changes in the company's creditworthiness, the ability of the company to make payments on the preferred stock, and changes in interest rates, typically declining in value if interest rates rise.

 

Sector focus risk. The Growth Fund may invest a larger portion of its assets in one or more sectors than many other mutual funds, and thus will be more susceptible to negative events affecting those sectors. For example, as of November 30, 2017, the Growth Fund invested significant amounts of its total assets in the Industrials and Information Technology sectors. Companies in the Industrials sector can be significantly affected by general economic trends, changes in consumer sentiment and spending, commodity prices, legislation, government regulation and spending, import controls, and worldwide competition. Companies in the Information Technology sector can be significantly affected by intense competition, consumer preferences, problems with product compatibility and government regulation.

 

Small-cap and mid-cap company risk. The securities of small-capitalization and mid-capitalization companies may be subject to more abrupt or erratic market movements and may have lower trading volumes or more erratic trading than securities of larger, more established companies or market averages in general. In addition, such companies typically are more likely to be adversely affected than large capitalization companies by changes in earning results, business prospects, investor expectations or poor economic or market conditions.
Risk Lose Money [Text] rr_RiskLoseMoney Before you decide whether to invest in the Growth Fund, carefully consider these risk factors associated with investing in the Growth Fund, which may cause investors to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Growth Fund by showing changes in the Growth Fund's performance from year to year for Institutional Class Shares and by showing how the average annual total returns of each class of the Growth Fund compare with the average annual total returns of a broad-based market index. Performance for classes other than those shown may vary from the performance shown to the extent the expenses for those classes differ. Updated performance information is available at the Growth Fund's website, www.riverbridge.com, or by calling the Growth Fund at 1-888-447-4470. The Growth Fund's past performance, before and after taxes, is not necessarily an indication of how the Growth Fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below provide some indication of the risks of investing in the Growth Fund by showing changes in the Growth Fund's performance from year to year for Institutional Class Shares and by showing how the average annual total returns of each class of the Growth Fund compare with the average annual total returns of a broad-based market index.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-888-447-4470
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.riverbridge.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Growth Fund's past performance, before and after taxes, is not necessarily an indication of how the Growth Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading

Calendar Year Total Return (before taxes) for Institutional Class Shares

For each calendar year at NAV
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Institutional Class Shares
Highest Calendar Quarter Return at NAV 11.80% Quarter Ended 3/31/2013
Lowest Calendar Quarter Return at NAV (5.22)% Quarter Ended 9/30/2015
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns

(for periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred After–tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class Shares only and after-tax returns for classes other than Institutional Class will vary from returns shown for Institutional Class.
Riverbridge Growth Fund | Investor Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol RIVRX
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Redemption fee if redeemed within 90 days of purchase (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption (1.00%)
Wire fee imst_WireFee $ 20
Overnight check delivery fee imst_Overnightcheckdeliveryfee 25
Retirement account fees (annual maintenance fee) rr_ShareholderFeeOther $ 15
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution and service (Rule 12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Shareholder service fees rr_Component1OtherExpensesOverAssets 0.03%
All other expenses rr_Component2OtherExpensesOverAssets 0.45%
Other expenses rr_OtherExpensesOverAssets 0.48%
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 1.49% [1]
Fees waived and/or expenses reimbursed rr_FeeWaiverOrReimbursementOverAssets (0.23%) [2]
Total annual fund operating expenses after waiving fees and/or reimbursing expenses rr_NetExpensesOverAssets 1.26% [1],[2]
One Year rr_ExpenseExampleYear01 $ 128
Three Years rr_ExpenseExampleYear03 448
Five Years rr_ExpenseExampleYear05 791
Ten Years rr_ExpenseExampleYear10 $ 1,760
1 Year rr_AverageAnnualReturnYear01 25.11%
5 Years rr_AverageAnnualReturnYear05 14.17%
Since Inception rr_AverageAnnualReturnSinceInception 14.17%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012
Riverbridge Growth Fund | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol RIVBX
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Redemption fee if redeemed within 90 days of purchase (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption (1.00%)
Wire fee imst_WireFee $ 20
Overnight check delivery fee imst_Overnightcheckdeliveryfee 25
Retirement account fees (annual maintenance fee) rr_ShareholderFeeOther $ 15
Management fees rr_ManagementFeesOverAssets 0.75%
Distribution and service (Rule 12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder service fees rr_Component1OtherExpensesOverAssets 0.03%
All other expenses rr_Component2OtherExpensesOverAssets 0.45%
Other expenses rr_OtherExpensesOverAssets 0.48%
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 1.24% [1]
Fees waived and/or expenses reimbursed rr_FeeWaiverOrReimbursementOverAssets (0.23%) [2]
Total annual fund operating expenses after waiving fees and/or reimbursing expenses rr_NetExpensesOverAssets 1.01% [1],[2]
One Year rr_ExpenseExampleYear01 $ 103
Three Years rr_ExpenseExampleYear03 371
Five Years rr_ExpenseExampleYear05 659
Ten Years rr_ExpenseExampleYear10 $ 1,480
Annual Return 2013 rr_AnnualReturn2013 37.57%
Annual Return 2014 rr_AnnualReturn2014 3.12%
Annual Return 2015 rr_AnnualReturn2015 4.37%
Annual Return 2016 rr_AnnualReturn2016 5.66%
Annual Return 2017 rr_AnnualReturn2017 25.42%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Calendar Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.80%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Calendar Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.22%)
1 Year rr_AverageAnnualReturnYear01 25.42%
5 Years rr_AverageAnnualReturnYear05 14.43%
Since Inception rr_AverageAnnualReturnSinceInception 14.43%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012
Riverbridge Growth Fund | After Taxes on Distributions | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 25.39% [3]
5 Years rr_AverageAnnualReturnYear05 13.99% [3]
Since Inception rr_AverageAnnualReturnSinceInception 13.99% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012 [3]
Riverbridge Growth Fund | After Taxes on Distributions and Sales | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 14.41% [3]
5 Years rr_AverageAnnualReturnYear05 11.54% [3]
Since Inception rr_AverageAnnualReturnSinceInception 11.54% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012 [3]
Riverbridge Growth Fund | Russell 3000 Growth Index (Reflects No Deductions for Fees, Expenses or Taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 29.59%
5 Years rr_AverageAnnualReturnYear05 17.16%
Since Inception rr_AverageAnnualReturnSinceInception 17.16%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012
Riverbridge Growth Fund | S&P 500 Index (Reflects No Deductions for Fees, Expenses or Taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 21.83%
5 Years rr_AverageAnnualReturnYear05 15.79%
Since Inception rr_AverageAnnualReturnSinceInception 15.79%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2012
Riverbridge Eco Leaders Fund  
Risk Return Abstract rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

SUMMARY SECTION - RIVERBRIDGE ECO LEADERS® FUND
Objective [Heading] rr_ObjectiveHeading

Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The investment objective of the Riverbridge Eco Leaders® Fund (the "Eco Leaders® Fund") is to seek 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 and hold shares of the Eco Leaders® 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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination March 31, 2028
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading

Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

The Eco Leaders® Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover 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 Eco Leaders® Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 13% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 13.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The "Total annual fund operating expenses" and "Total annual fund operating expenses after waiving fees and/or reimbursing expenses" do not correlate to the ratio of expenses to average net assets appearing in the financial highlights table, which reflects only the operating expenses of the Eco Leaders® Fund and does not include acquired fund fees and expenses.
Expense Example [Heading] rr_ExpenseExampleHeading

Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Eco Leaders® Fund with the cost of investing in other mutual funds.

 

The example assumes that you invest $10,000 in the Eco Leaders® Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Eco Leaders® Fund's operating expenses remain the same.

 

Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the Eco Leaders® Fund invests at least 80% of its net assets (plus borrowings for investment purposes) in equity securities of "Eco Leader" companies, which are companies that Riverbridge Partners, LLC (the "Advisor"), the Eco Leaders® Fund's advisor, believes are transformational and ethical (i.e., companies that position themselves for sustainable market leadership, long-term growth, and capital appreciation), while demonstrating environmental stewardship, social responsibility and corporate governance best practices.

 

The Eco Leaders® Fund's investments in equity securities may include common stock, preferred stock and convertible securities. While the Eco Leaders® Fund invests primarily in equity securities of U.S. issuers, it may invest in securities of foreign (i.e., non-U.S.) issuers. The Eco Leaders® Fund's investments in foreign securities are primarily comprised of U.S. dollar-denominated securities of foreign issuers traded in the United States and American Depositary Receipts ("ADRs"). ADRs are receipts that represent interests in foreign securities held on deposit by U.S. banks. The Eco Leaders® Fund may invest in companies of any size, including small- and mid-capitalization companies. The Eco Leaders® Fund intends to invest in a portfolio of securities typically spread across many economic sectors, although from time to time, the Fund may have significant portion of its assets in one or more market sectors such as the information technology. In seeking to diversify the Eco Leaders® Fund's portfolio, the Fund's advisor focuses on the portfolio's earnings catalysts rather than formal limitation of exposure to market sectors. The advisor seeks to limit the portfolio exposure of the Eco Leaders® Fund to a common earnings catalyst (e.g., consumer spending) to no more than 20% of the Fund's net assets. The Eco Leaders® Fund may invest in investment grade convertible securities of any maturity. Investment grade securities are those rated at the time of acquisition Baa3 or higher by Moody's Investors Service, Inc. ("Moody's"), or BBB- or higher by Standard & Poor's ("S&P"), or Fitch Ratings Ltd. ("Fitch") or, if unrated by S&P, Moody's or Fitch, determined by the Advisor to be of comparable quality.

 

The Advisor believes that earnings power determines the value of a franchise. The Advisor focuses on companies that it views as building their earnings power and intrinsic, or actual, values over long periods of time. The Advisor uses a bottom-up approach that seeks to identify high quality, well-managed growth companies that demonstrate the ability to sustain strong secular earnings growth regardless of overall economic conditions. This fundamental approach includes a rigorous research and due diligence process including a thorough assessment of a company's culture and sustainable market leadership through direct interactions with a company's management team. In addition, the Advisor performs an assessment of the company through interactions with the company's management team, as well as a peer-review process that includes interactions with the company's competitors, suppliers, partners and/or customers. The Advisor believes these interactions allow for the opportunity to evaluate key aspects of the company's environmental, social and governance profiles. In selecting the Eco Leaders® Fund's investments the Advisor selects companies based on the Advisor's investment process and criteria, which includes environmental, social and governance standards.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration The Eco Leaders® Fund intends to invest in a portfolio of securities typically spread across many economic sectors, although from time to time, the Fund may have significant portion of its assets in one or more market sectors such as the information technology.
Risk [Heading] rr_RiskHeading

Principal Risks of Investing
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

Risk is inherent in all investing and you could lose money by investing in the Fund. A summary description of certain principal risks of investing in the Eco Leaders® Fund is set forth below. Before you decide whether to invest in the Eco Leaders® Fund, carefully consider these risk factors associated with investing in the Eco Leaders® Fund, which may cause investors to lose money. There can be no assurance that the Eco Leaders® Fund will achieve its investment objective.

 

Convertible securities risk. Convertible securities are subject to market and interest rate risk and credit risk. When the market price of the equity security underlying a convertible security decreases the convertible security tends to trade on the basis of its yield and other fixed income characteristics, and is more susceptible to credit and interest rate risks. When the market price of such equity security rises, the convertible security tends to trade on the basis of its equity conversion features and be more exposed to market risk. Convertible securities are typically issued by smaller capitalized companies with stock prices that may be more volatile than those of other companies.

 

Environmental, social and governance policy risk. The Eco Leaders® Fund's investment focus on environmental factors and social and governance practices could cause it to make or avoid investments that could result in the Eco Leaders® Fund underperforming relative to funds that do not have such focus.

 

Equity risk. The value of the equity securities held by the Eco Leaders® Fund may fall due to general market and economic conditions, perceptions regarding the industries in which the issuers of securities held by the Eco Leaders® Fund participate, or factors relating to specific companies in which the Fund invests.

 

Foreign investment risk. The prices of foreign securities may be more volatile than the prices of securities of U.S. issuers because of economic and social conditions abroad, political developments, and changes in the regulatory environments of foreign countries. In addition, changes in exchange rates and interest rates may adversely affect the values of the Eco Leaders® Fund's foreign investments. Foreign companies are generally subject to different legal and accounting standards than U.S. companies, and foreign financial intermediaries may be subject to less supervision and regulation than U.S. financial firms. Foreign securities include American Depository Receipts ("ADRs"). Unsponsored ADRs are organized independently and without the cooperation of the foreign issuer of the underlying securities, and involve additional risks because U.S. reporting requirements do not apply. In addition, the issuing bank may deduct shareholder distribution, custody, foreign currency exchange, and other fees from the payment of dividends.

 

Growth-oriented investment strategies risk. Growth funds generally focus on stocks of companies believed to have above-average potential for growth in revenue and earnings. Growth securities typically are very sensitive to market movements because their market prices frequently reflect projections of future earnings or revenues, and when it appears that those expectations will not be met, the prices of growth securities typically fall.

 

Management and strategy risk. The value of your investment depends on the judgment of the Advisor about the quality, relative yield, value or market trends affecting a particular security, industry, sector or region, which may prove to be incorrect.

 

Market risk. The market price of a security or instrument may decline, sometimes rapidly or unpredictably, due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic or political conditions throughout the world, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. The market value of a security or instrument also may decline because of factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry.

 

Preferred stock risk. Preferred stock represents an equity interest in a company that generally entitles the holder to receive, in preference to the holders of other stocks such as common stock, dividends and a fixed share of the proceeds resulting from a liquidation of the company. The market value of preferred stock is subject to company-specific and market risks applicable generally to equity securities and is also sensitive to changes in the company's creditworthiness, the ability of the company to make payments on the preferred stock, and changes in interest rates, typically declining in value if interest rates rise.

 

Sector focus risk. The Eco Leaders® Fund may invest a larger portion of its assets in one or more sectors than many other mutual funds, and thus will be more susceptible to negative events affecting those sectors. For example, as of November 30, 2017, the Eco Leaders® Fund invested significant amounts of its total assets in the Industrials and Information Technology sectors. Companies in the Industrials sector can be significantly affected by general economic trends, changes in consumer sentiment and spending, commodity prices, legislation, government regulation and spending, import controls, and worldwide competition. Companies in the Information Technology sector can be significantly affected by intense competition, consumer preferences, problems with product compatibility and government regulation.

 

Small-cap and mid-cap company risk. The securities of small-capitalization and mid-capitalization companies may be subject to more abrupt or erratic market movements and may have lower trading volumes or more erratic trading than securities of larger, more established companies or market averages in general. In addition, such companies typically are more likely to be adversely affected than large capitalization companies by changes in earning results, business prospects, investor expectations or poor economic or market conditions.
Risk Lose Money [Text] rr_RiskLoseMoney Before you decide whether to invest in the Eco Leaders® Fund, carefully consider these risk factors associated with investing in the Eco Leaders® Fund, which may cause investors to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading

Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Eco Leaders® Fund by showing changes in the Eco Leaders® Fund's performance from year to year for Institutional Class Shares and by showing how the average annual total returns of each class of the Eco Leaders® Fund compare with the average annual total returns of a broad-based market index. Performance for classes other than those shown may vary from the performance shown to the extent the expenses for those classes differ. Updated performance information is available at the Eco Leaders® Fund's website, www.riverbridge.com, or by calling the Eco Leaders® Fund at 1-888-447-4470. The Eco Leaders® Fund's past performance, before and after taxes, is not necessarily an indication of how the Eco Leaders® Fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The bar chart and table below provide some indication of the risks of investing in the Eco Leaders® Fund by showing changes in the Eco Leaders® Fund's performance from year to year for Institutional Class Shares and by showing how the average annual total returns of each class of the Eco Leaders® Fund compare with the average annual total returns of a broad-based market index.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-888-447-4470
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.riverbridge.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Eco Leaders® Fund's past performance, before and after taxes, is not necessarily an indication of how the Eco Leaders® Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading

Calendar Year Total Return (before taxes) for Institutional Class Shares

For each calendar year at NAV
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
 Institutional Class Shares
Highest Calendar Quarter Return at NAV 7.71% Quarter Ended 12/31/2017
Lowest Calendar Quarter Return at NAV (5.34)% Quarter Ended 9/30/2015
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns

(for periods ended December 31, 2017)
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred After–tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Institutional Class Shares only and after-tax returns for classes other than Institutional Class will vary from returns shown for Institutional Class.
Riverbridge Eco Leaders Fund | Investor Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol ECOLX
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Redemption fee if redeemed within 90 days of purchase (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption (1.00%)
Wire fee imst_WireFee $ 20
Overnight check delivery fee imst_Overnightcheckdeliveryfee 25
Retirement account fees (annual maintenance fee) rr_ShareholderFeeOther $ 15
Management fees rr_ManagementFeesOverAssets 0.90%
Distribution and service (Rule 12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Shareholder service fees rr_Component1OtherExpensesOverAssets 0.03%
All other expenses rr_Component2OtherExpensesOverAssets 10.06%
Other expenses rr_OtherExpensesOverAssets 10.09%
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 11.25% [4]
Fees waived and/or expenses reimbursed rr_FeeWaiverOrReimbursementOverAssets (9.84%) [5]
Total annual fund operating expenses after waiving fees and/or reimbursing expenses rr_NetExpensesOverAssets 1.41% [4],[5]
One Year rr_ExpenseExampleYear01 $ 144
Three Years rr_ExpenseExampleYear03 446
Five Years rr_ExpenseExampleYear05 771
Ten Years rr_ExpenseExampleYear10 $ 1,691
1 Year rr_AverageAnnualReturnYear01 23.72%
Since Inception rr_AverageAnnualReturnSinceInception 10.32%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Riverbridge Eco Leaders Fund | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
Trading Symbol dei_TradingSymbol RIVEX
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOfferingPrice none
Redemption fee if redeemed within 90 days of purchase (as a percentage of amount redeemed) rr_RedemptionFeeOverRedemption (1.00%)
Wire fee imst_WireFee $ 20
Overnight check delivery fee imst_Overnightcheckdeliveryfee 25
Retirement account fees (annual maintenance fee) rr_ShareholderFeeOther $ 15
Management fees rr_ManagementFeesOverAssets 0.90%
Distribution and service (Rule 12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Shareholder service fees rr_Component1OtherExpensesOverAssets 0.03%
All other expenses rr_Component2OtherExpensesOverAssets 10.06%
Other expenses rr_OtherExpensesOverAssets 10.09%
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 11.00% [4]
Fees waived and/or expenses reimbursed rr_FeeWaiverOrReimbursementOverAssets (9.84%) [5]
Total annual fund operating expenses after waiving fees and/or reimbursing expenses rr_NetExpensesOverAssets 1.16% [4],[5]
One Year rr_ExpenseExampleYear01 $ 118
Three Years rr_ExpenseExampleYear03 368
Five Years rr_ExpenseExampleYear05 638
Ten Years rr_ExpenseExampleYear10 $ 1,409
Annual Return 2015 rr_AnnualReturn2015 2.48%
Annual Return 2016 rr_AnnualReturn2016 6.39%
Annual Return 2017 rr_AnnualReturn2017 23.98%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Calendar Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2017
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 7.71%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Calendar Quarter
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.34%)
1 Year rr_AverageAnnualReturnYear01 23.98%
Since Inception rr_AverageAnnualReturnSinceInception 10.57%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Riverbridge Eco Leaders Fund | After Taxes on Distributions | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 23.98% [3]
Since Inception rr_AverageAnnualReturnSinceInception 10.23% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014 [3]
Riverbridge Eco Leaders Fund | After Taxes on Distributions and Sales | Institutional Class Shares  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 13.58% [3]
Since Inception rr_AverageAnnualReturnSinceInception 8.11% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014 [3]
Riverbridge Eco Leaders Fund | Russell 3000 Growth (Reflects No Deductions for Fees, Expenses or Taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 29.59%
Since Inception rr_AverageAnnualReturnSinceInception 13.51%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
Riverbridge Eco Leaders Fund | S&P 500 Index (Reflects No Deductions for Fees, Expenses or Taxes)  
Risk Return Abstract rr_RiskReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 21.83%
Since Inception rr_AverageAnnualReturnSinceInception 11.41%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2014
[1] The "Total annual fund operating expenses" and "Total annual fund operating expenses after waiving fees and/or reimbursing expenses" do not correlate to the ratio of expenses to average net assets appearing in the financial highlights table, which reflects only the operating expenses of the Growth Fund and does not include acquired fund fees and expenses.
[2] The Growth Fund's advisor has contractually agreed to waive its fees and/or pay for operating expenses of the Fund to ensure that total annual fund operating expenses (excluding any taxes, leverage interest, brokerage commissions, dividend and interest expenses on short sales, acquired fund fees and expenses (as determined in accordance with SEC Form N-1A), expenses incurred in connection with any merger or reorganization and extraordinary expenses such as litigation expenses) do not exceed 1.25% and 1.00% of the average daily net assets of the Growth Fund's Investor Class and Institutional Class shares, respectively. This agreement is in effect until March 31, 2019, and it may be terminated before that date only by the Trust's Board of Trustees. The Growth Fund's advisor is permitted to seek reimbursement from the Growth Fund, subject to certain limitations, of fees waived or payments made to the Growth Fund for a period ending three full fiscal years after the date of the waiver or payment. This reimbursement may be requested from the Growth Fund if the reimbursement will not cause the Growth Fund's annual expense ratio to exceed the lesser of (a) the expense limitation in effect at the time such fees were waived or payments made, or (b) the expense limitation in effect at the time of the reimbursement.
[3] After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After–tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Institutional Class Shares only and after-tax returns for classes other than Institutional Class will vary from returns shown for Institutional Class.
[4] The "Total annual fund operating expenses" and "Total annual fund operating expenses after waiving fees and/or reimbursing expenses" do not correlate to the ratio of expenses to average net assets appearing in the financial highlights table, which reflects only the operating expenses of the Eco Leaders® Fund and does not include acquired fund fees and expenses.
[5] The Eco Leaders® Fund's advisor has contractually agreed to waive its fees and/or pay for operating expenses of the Fund to ensure that total annual fund operating expenses (excluding any taxes, leverage interest, brokerage commissions, dividend and interest expenses on short sales, acquired fund fees and expenses (as determined in accordance with SEC Form N-1A), expenses incurred in connection with any merger or reorganization, and extraordinary expenses such as litigation expenses) do not exceed 1.40% and 1.15% of the average daily net assets of the Eco Leaders® Fund's Investor Class and Institutional Class shares, respectively. This agreement is in effect until March 31, 2028, and it may be terminated before that date only by the Trust's Board of Trustees. The Eco Leaders® Fund's advisor is permitted to seek reimbursement from the Eco Leaders® Fund, subject to certain limitations, of fees waived or payments made to the Eco Leaders® Fund for a period ending three full fiscal years after the date of the waiver or payment. This reimbursement may be requested from the Eco Leaders® Fund if the reimbursement will not cause the Eco Leaders® Fund's annual expense ratio to exceed the lesser of (a) the expense limitation in effect at the time such fees were waived or payments made, or (b) the expense limitation in effect at the time of the reimbursement.