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RMB Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB Fund (the “Fund”) seeks capital appreciation, mainly long term. Income is generally of lesser importance, meaning that it is a secondary goal. There can be no assurance that the Fund will be successful in achieving its investment objective.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 your family invest, or agree to invest in the future, at least $50,000 in the Fund. More information about these and other discounts is available from your financial intermediary and in the “Choosing a Share Class” section on page 50 of this prospectus, Appendix A to this prospectus, and the “Purchase and Redemption of Shares” section on page 30 of the Fund’s Statement of Additional Information.
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 pays 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 12% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 12.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock These Examples are intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The first Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods, followed by an Example that assumes you do not redeem your shares at the end of the periods. The Examples also assume that your investment has a 5% return each year and that the Fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock You would pay the following expenses if you did not redeem your shares:
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund pursues its investment objective by investing in a diverse portfolio primarily consisting of common stocks.
The Fund generally invests in high quality companies of all market capitalizations with a focus on businesses that have sustainable, long term competitive advantages. Portfolio companies may range from small and mid-sized businesses that are earlier in their growth life cycle, to larger more mature companies that return capital to shareholders through increasing dividend payments and share buy-backs. High quality companies are generally defined as companies with product leadership, that have potential for sustained operating and revenue growth and that are run by strong management teams that allocate shareholder capital wisely and align their economic interests with shareholders. The Fund employs a long-term approach when selecting stocks and seeks to own businesses that have durable franchises that can weather the ups and downs of volatile business cycles.
From time to time, the Fund may invest in companies that are experiencing unusual and possibly unique developments. Potential investments in the stock of these companies are usually the result of companies uncovered in the research process that do not meet the criteria employed by the Fund but may have opportunities for significant returns. These companies are deemed “special situations.” Special situations include companies going through reorganizations, recapitalizations, mergers, spin-offs, or facing resolutions of litigation, management team changes, or important technological improvements or discoveries.
The Fund’s investment strategy seeks to build wealth over time by purchasing the stock of high quality growth companies that are deemed to be trading below their intrinsic value. The Fund’s portfolio is constructed on a stock by stock basis. Position sizes are determined based on current portfolio characteristics, valuation, the risk/reward profile and confidence in the company. The Fund may consider larger macro-economic trends, and will occasionally pursue investment themes across multiple holdings, when constructing the portfolio. The Fund seeks to manage risk by diversifying its holdings across sectors and industries. The Fund typically owns 30-40 stocks which is intended to allow for enough diversification to minimize risk, but enough concentration to allow the highest conviction ideas to impact the portfolio. A position will be sold if a core tenet for ownership has been violated, if valuation discounts substantially all of the upside of a company, or if a better use of capital presents itself.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
Any of the following situations could cause the Fund to lose money or underperform in comparison with its peer group:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Large-Cap Companies Risk — Larger, more established companies may be unable to respond quickly to new competitive challenges, such as changes in consumer tastes or innovative smaller competitors. Also, large-cap companies are sometimes unable to attain the high growth rates of successful, smaller companies, especially during extended periods of economic expansion.
•Dividend Risk —This is the risk that an issuer of stock held by the Fund may choose not to declare a dividend or the dividend rate might not remain at current levels. Dividend paying stocks might not experience the same level of earnings growth or capital appreciation as non-dividend paying stocks. The Fund’s performance during a broad market advance could suffer because dividend paying stocks may not experience the same capital appreciation as non-dividend paying stocks.
•Small- and Mid-Cap Companies Risk — The Fund may invest in the securities of companies with small- and mid-capitalizations, which can involve greater risk and the possibility of greater portfolio volatility than investments in securities of large-capitalization companies. Historically, stocks of small- and mid-capitalization companies and recently organized companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such stocks. Small- and mid-capitalization companies may have limited product lines and financial resources and may depend upon a limited or less experienced management group. The securities of small-capitalization companies trade in the over-the-counter markets or on regional exchanges and may not be traded daily or in the volume typical of trading on a national securities exchange, which may make these securities more difficult to value and to sell.
•Growth Investing Risk — Growth stocks may fall out of favor with investors and underperform other asset types during given periods. A company may never achieve the earnings growth the team anticipated.
•Special Situations Risk — The Fund will seek to benefit from “special situations,” such as mergers, reorganizations, or other unusual events expected to affect a particular issuer. There is a risk that the “special situation” might not occur or involve longer time frames than originally expected, which could have a negative impact on the price of the issuer’s securities and fail to produce gains or produce a loss for the Fund.
Risk Lose Money [Text] rr_RiskLoseMoney Any of the following situations could cause the Fund to lose money or underperform in comparison with its peer group:
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5 and 10 years compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. Returns shown for periods prior to July 1, 2016 were generated under the management of the Fund’s former investment adviser. The returns in the bar chart do not include the effect of Class A shares’ front-end sales charges. The returns in the performance table reflect any applicable sale charges. These figures would be lower if they reflected such sales charges. The Fund’s performance figures assume that all distributions were reinvested in the Fund and do not reflect the deduction of the Fund’s maximum sales charges or its annual operating expenses. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5 and 10 years compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB Fund – Return for Class A Shares
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads The Fund’s performance figures assume that all distributions were reinvested in the Fund and do not reflect the deduction of the Fund’s maximum sales charges or its annual operating expenses.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter: 22.00% in 2nd Quarter of 2020
Worst Quarter: -23.73% in 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The returns in the performance table reflect any applicable sale charges. These figures would be lower if they reflected such sales charges.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, 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; after-tax returns for Class C and Class I shares will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”). The after-tax returns are shown only for Class A shares; after-tax returns for Class C and Class I shares will vary.
RMB Fund | S&P 500® Index Total Return (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel S&P 500® Index (total return)2(reflects no deduction of fees, expenses or taxes) [1]
1 Year rr_AverageAnnualReturnYear01 28.71% [1]
5 Years rr_AverageAnnualReturnYear05 18.47% [1]
10 Years rr_AverageAnnualReturnYear10 16.55% [1]
RMB Fund | Russell 3000® Index (total return) (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 3000® Index (total return)2(reflects no deduction of fees, expenses or taxes) [1]
1 Year rr_AverageAnnualReturnYear01 25.66% [1]
5 Years rr_AverageAnnualReturnYear05 17.97% [1]
10 Years rr_AverageAnnualReturnYear10 16.30% [1]
RMB Fund | Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBHX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 608
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 838
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,086
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,795
Annual Return 2011 rr_AnnualReturn2011 5.40%
Annual Return 2012 rr_AnnualReturn2012 12.61%
Annual Return 2013 rr_AnnualReturn2013 24.28%
Annual Return 2014 rr_AnnualReturn2014 8.04%
Annual Return 2015 rr_AnnualReturn2015 1.52%
Annual Return 2016 rr_AnnualReturn2016 1.32%
Annual Return 2017 rr_AnnualReturn2017 22.49%
Annual Return 2018 rr_AnnualReturn2018 (2.84%)
Annual Return 2019 rr_AnnualReturn2019 37.16%
Annual Return 2020 rr_AnnualReturn2020 15.93%
Annual Return 2021 rr_AnnualReturn2021 29.99%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 22.00%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (23.73%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 23.49%
5 Years rr_AverageAnnualReturnYear05 18.51%
10 Years rr_AverageAnnualReturnYear10 13.77%
RMB Fund | Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 21.80%
5 Years rr_AverageAnnualReturnYear05 15.85%
10 Years rr_AverageAnnualReturnYear10 11.15%
RMB Fund | Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 15.06%
5 Years rr_AverageAnnualReturnYear05 14.17%
10 Years rr_AverageAnnualReturnYear10 10.49%
RMB Fund | Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBJX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.87%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 290
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 588
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,011
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,190
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 190
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 588
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,011
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,190
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 28.03%
5 Years rr_AverageAnnualReturnYear05 18.84%
10 Years rr_AverageAnnualReturnYear10 13.50%
RMB Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBGX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.87%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 89
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 278
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 482
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,073
Label rr_AverageAnnualReturnLabel Total Return Before Taxes [2]
1 Year rr_AverageAnnualReturnYear01 30.31% [2]
5 Years rr_AverageAnnualReturnYear05 20.02% [2]
10 Years rr_AverageAnnualReturnYear10 14.50% [2]
RMB Mendon Financial Services Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB Mendon Financial Services Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB Mendon Financial Services Fund (the “Fund”) seeks capital appreciation. There can be no assurance that the Fund will be successful in achieving its investment objective.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 your family invest, or agree to invest in the future, at least $50,000 in the Fund. More information about these and other discounts is available from your financial intermediary and in the “Choosing a Share Class” section on page 50 of this prospectus, Appendix A to this prospectus, and the “Purchase and Redemption of Shares” section on page 30 of the Fund’s Statement of Additional Information.
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 pays 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 70% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 70.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees Total Annual Fund Operating Expenses do not correlate to the Ratio of Expenses to Average Net Assets in the Financial Highlights section of the statutory prospectus, which reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (“AFFE”).
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock These Examples are intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The first Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods, followed by an Example that assumes you do not redeem your shares at the end of the periods. The Examples also assume that your investment has a 5% return each year and that the Fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption Narrative [Text Block] rr_ExpenseExampleNoRedemptionNarrativeTextBlock You would pay the following expenses if you did not redeem your shares:
Strategy [Heading] rr_StrategyHeading PRINCIPAL INVESTMENT STRATEGIES
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in stocks of U.S. companies that are in the financial services industry. The Fund includes the market value of derivatives that provide exposure to the financial services industry in determining compliance with the Fund’s 80% investment policy. The Fund may invest in companies of any size, but, under normal conditions, the Fund invests primarily in mid-, small- and micro-capitalization financial services companies. For purposes of selecting investments, the Fund defines the financial services industry broadly. It includes (but is not limited to) the following:
•Banks
•Insurance companies
•Consumer and commercial finance companies
•Securities brokerage firms and electronic trading networks
•Investment management and advisory firms
•Financial conglomerates
•Financial technology companies

Ordinarily, the Fund’s portfolio will be invested primarily in common stocks. In selecting stocks, the Fund’s sub-adviser uses a combination of growth and value style investment criteria. Growth criteria include such items as capable management, attractive business niches, sound financial and accounting practices and/or demonstrated ability to sustain growth in revenues, earnings and cash flow. Value criteria include companies that appear to be undervalued based on their balance sheets or individual circumstances, temporarily distressed, or poised for a merger or acquisition.
The Fund may also invest in companies that may experience unusual and possibly unique developments, or “special situations,” which may create a special opportunity for significant returns. Special situations include: significant technological improvements or discoveries; reorganizations, recapitalizations or mergers; favorable resolutions of litigation; new management or material changes in company policies; and actual or potential changes in control of a company. These companies are deemed “special situations.” Special situations include companies going through reorganizations, recapitalizations, mergers, spin-offs or facing resolutions of litigation, management team changes or important technological improves or discoveries.
The portfolio manager constructs the Fund’s portfolio using both a top-down and bottom-up analysis. Examples of top-down analysis include the study of interest rates, credit trends and other macroeconomic factors that broadly affect the financial services industry. Examples of bottom-up analysis include industry screens, sell-side company research reports, company models and other fundamental research that are used to construct the Fund’s portfolio on a stock-by-stock basis. The sub-adviser attempts to identify how various financial services sub-sectors and the individual companies therein will move in reaction to market events. Each potential investment is evaluated by weighing its potential for gain against its associated risks. Because of the way the sub-adviser constructs the Fund’s portfolio, there may be times when the Fund’s investments are focused in one or more financial services sub-sectors and/or a limited number of regions of the U.S.
The Fund may sell securities for a variety of reasons, such as to secure gains, limit losses or redeploy assets into other opportunities.
The Fund may also use futures and options on securities, indices and other derivatives (a type of instrument whose value is determined by reference to the value or the change in value of one or more securities, indices or other financial instruments) to hedge against market changes or as a substitute for securities transactions. It may also use derivatives in attempts to profit from anticipated market and security movements. Effective August 18, 2022, the Fund will limit its derivatives exposure to 10% of its net assets. The Fund expects that its primary investments in derivatives will be in written covered call options and long call options. As the writer of a covered call option, the Fund forgoes, during the option’s life, the opportunity to profit from increases in the market value of the security
covering the call option above the sum of the premium and the strike price of the call, but has retained the risk of loss should the price of the underlying security decline. Long call option purchases allow the option holder to be exposed to the general market characteristics of a security without the outlay of capital necessary to own the security.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Financial Services Risk — A fund that focuses its investments in specific industries or sectors is more susceptible to developments affecting those industries and sectors than a more broadly diversified fund would be. Because the Fund invests significantly in financial services companies, the Fund may perform poorly during a downturn in the financial services industry. The financial services industry can be significantly affected by changes in interest rates, the rate of corporate and consumer debt defaults, the availability and cost of borrowing and raising capital, reduced credit market liquidity, regulatory changes, price competition, and general economic and market conditions. Changing interest rates could reduce the profitability of certain types of companies in the financial services industry. Financial services companies may have concentrated portfolios, such as a high level of loans to one or more industries or sectors, which makes them vulnerable to economic conditions that affect such industries or sectors. The COVID-19 pandemic has had, and may continue to have, a significant negative impact on economies and financial markets worldwide, resulting in higher debt defaults, loan write-offs, and government intervention, historically low interest rates, and potentially the failure of some financial institutions, each of which would reduce investment performance of financial services companies.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Derivatives Risk — The use of derivatives presents risks different from, and possibly greater than, the risks associated with investing directly in traditional securities as well as increased transaction costs. The use of derivatives can lead to losses because of adverse movements in the price or value of the underlying asset, reference rate or index. Also, a liquid market may not always exist for the Fund’s derivative positions at times when the Fund might wish to terminate or sell such positions.
•Call and Put Options Risk — A call option obligates the writer (or seller) of the option to sell a specified asset to the holder of the option at a specified price when the holder exercises the option prior to expiration. A put option obligates the writer (or seller) of the option to buy a specified asset from the holder of the option at a specified price when the holder exercises the option prior to expiration. Writing covered call options may deprive the Fund of the opportunity to profit from an increase in the market price of the reference asset. Writing covered put options may subject the Fund to a decrease in the market price of the reference asset. Purchasing an option subjects the buyer to the risk that the benefit received from exercising the option, if any, will not exceed the premium paid to purchase the option. Options are wasting assets and expire, and as a result can expose the Fund to significant loss. The Fund will have no control over the exercise of the call options it writes and therefore may be forced to realize capital gains or losses at inopportune times.
•Futures Risk — The risk of loss in trading futures contracts and in writing futures options can be substantial because of the low margin deposits required, the extremely high degree of leverage involved in futures and options pricing, and the potential high volatility of the futures markets. As a result, a relatively small price movement in a futures position may result in immediate and substantial loss (or gain) for the Fund, and losses could exceed the amount invested in the position. The Fund bears the risk that the adviser will incorrectly predict future market trends. If the adviser attempts to use a futures contract or a futures option as a hedge against, or as a substitute for, a portfolio investment, the Fund will be exposed to the risk that the futures position will have or will develop imperfect or no correlation with the portfolio investment. This could cause substantial losses for the Fund. The Fund could suffer losses if it is unable to close out a futures contract or a futures option because of an illiquid secondary market, and there can be no assurance that a liquid secondary market will exist for any particular futures product at any specific time.
•Small- and Mid-Cap Companies Risk — The Fund may invest in the securities of companies with small- and mid-capitalizations, which can involve greater risk and the possibility of greater portfolio volatility than investments in securities of large-capitalization companies. Historically, stocks of small- and mid-capitalization companies and recently organized companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such stocks. Small- and mid-capitalization companies may have limited product lines and financial resources and may depend upon a limited or less experienced management group. The securities of small-capitalization companies trade in the over-the-counter markets or on regional exchanges and may not be traded daily or in the volume typical of trading on a national securities exchange, which may make these securities more difficult to value and to sell.
•Growth Investing Risk — Growth stocks may fall out of favor with investors and underperform other asset types during given periods. A company may never achieve the earnings growth the adviser anticipated.
•Value Investing Risk — Value stocks may not increase in price, may not issue the anticipated stock dividends or may decline in price, based upon the market’s belief of the issuer’s intrinsic worth.
•Large-Cap Companies Risk — Larger, more established companies may be unable to respond quickly to new competitive challenges, such as changes in consumer tastes or innovative smaller competitors. Also, large-cap companies are sometimes unable to attain the high growth rates of successful, smaller companies, especially during extended periods of economic expansion.
•Micro-Cap Companies Risk — Micro-cap stocks have a market capitalization of less than $300 million. Micro-cap companies may be less financially secure than large, mid or small capitalization companies. Micro-cap companies may be in the early stage of development or newly formed with limited markets or product lines. There may also be less public information about micro-cap companies. In addition, micro-cap companies that rely on smaller management teams may be vulnerable to key personnel losses. Micro-cap stock prices also may be more volatile than large, mid or small-cap stocks, may have lower trading volume and lower degree of liquidity which makes these securities difficult to value and to sell. The securities of micro-cap companies may not be traded daily. As a result, some of the Fund’s holdings may be considered or become illiquid.
•Special Situations Risk — The Fund will seek to benefit from “special situations,” such as mergers, reorganizations, or other unusual events expected to affect a particular issuer. There is a risk that the “special situation” might not occur or involve longer time frames than originally expected, which could have a negative impact on the price of the issuer’s securities and fail to produce gains or produce a loss for the Fund.
Risk Lose Money [Text] rr_RiskLoseMoney The Fund’s share price fluctuates, which means you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5 and 10 years compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. The returns in the bar chart do not include the effect of Class A shares’ front-end sales charges. These figures would be lower if they reflected such sales charges. The returns in the performance table reflect any applicable sales charges. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5 and 10 years compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB Mendon Financial Services Fund – Return for Class A Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: 44.15% in the 4th Quarter of 2020 Worst Quarter: -42.59% in the 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads These figures would be lower if they reflected such sales charges. The returns in the performance table reflect any applicable sales charges.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, such as 401(k) plans or IRAs.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown The after-tax returns are shown only for Class A shares; after-tax returns for Class C and Class I shares will vary.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or IRAs. The after-tax returns are shown only for Class A shares; after-tax returns for Class C and Class I shares will vary.
RMB Mendon Financial Services Fund | NASDAQ Bank Index Total Return (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel NASDAQ Bank Index Total Return2(reflects no deduction of fees, expenses or taxes) [3]
1 Year rr_AverageAnnualReturnYear01 42.91% [3]
5 Years rr_AverageAnnualReturnYear05 7.76% [3]
10 Years rr_AverageAnnualReturnYear10 14.44% [3]
RMB Mendon Financial Services Fund | Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBKX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.27% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 623
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 883
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,162
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,957
Annual Return 2011 rr_AnnualReturn2011 (10.34%)
Annual Return 2012 rr_AnnualReturn2012 23.41%
Annual Return 2013 rr_AnnualReturn2013 35.42%
Annual Return 2014 rr_AnnualReturn2014 11.11%
Annual Return 2015 rr_AnnualReturn2015 20.43%
Annual Return 2016 rr_AnnualReturn2016 29.74%
Annual Return 2017 rr_AnnualReturn2017 11.99%
Annual Return 2018 rr_AnnualReturn2018 (17.02%)
Annual Return 2019 rr_AnnualReturn2019 22.80%
Annual Return 2020 rr_AnnualReturn2020 (5.73%)
Annual Return 2021 rr_AnnualReturn2021 56.44%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 44.15%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (42.59%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 48.62%
5 Years rr_AverageAnnualReturnYear05 9.84%
10 Years rr_AverageAnnualReturnYear10 16.59%
RMB Mendon Financial Services Fund | Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 48.01%
5 Years rr_AverageAnnualReturnYear05 9.08%
10 Years rr_AverageAnnualReturnYear10 15.96%
RMB Mendon Financial Services Fund | Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 28.99%
5 Years rr_AverageAnnualReturnYear05 7.55%
10 Years rr_AverageAnnualReturnYear10 13.94%
RMB Mendon Financial Services Fund | Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBNX
Maximum Deferred Sales Charge (as a percentage of Offering Price) rr_MaximumDeferredSalesChargeOverOfferingPrice 1.00%
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.02% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 305
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 634
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,088
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 2,348
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 205
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 634
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 1,088
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 2,348
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 54.28%
5 Years rr_AverageAnnualReturnYear05 10.14%
10 Years rr_AverageAnnualReturnYear10 16.30%
RMB Mendon Financial Services Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBLX
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.03%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.02% [4]
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 104
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 325
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 563
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,248
Label rr_AverageAnnualReturnLabel Total Return Before Taxes [5]
1 Year rr_AverageAnnualReturnYear01 56.84% [5]
5 Years rr_AverageAnnualReturnYear05 11.42% [5]
10 Years rr_AverageAnnualReturnYear10 17.42% [5]
RMB International Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB International Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB International Fund (the “Fund”) seeks long-term capital appreciation. There can be no assurance that the Fund will be successful in achieving its investment objective.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 Fee Table or the Example below.
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 pays 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 21% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 21.00%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The 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 assumes that you invest $10,000 in the 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 Fund’s operating expenses remain the same.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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
The Fund pursues its investment objective by investing, under normal conditions, in at least three different countries and at least 40% of its total assets in securities of non-U.S. issuers organized or having their principal place of business outside the U.S. or doing a substantial amount (more than 50%) of business outside the U.S. Investments in exchange-traded funds (“ETFs”) based on non-U.S. market indices are considered investments outside the U.S. for purposes of the 40% requirement noted above.
The Fund’s non-U.S. investments will be primarily in developed markets, but the Fund may invest in emerging markets. As of the date of this Prospectus, the Fund’s investment adviser believes that developed markets outside the United States include, but may not be limited to, the following: Austria, Australia, Belgium, Canada, Denmark, Finland, France, Germany, Hong Kong, Ireland, Israel, Italy, Japan, Netherlands, New Zealand, Norway, Portugal, Singapore, Spain, Sweden, Switzerland and the United Kingdom. The Fund considers emerging markets to be markets located in countries classified as emerging or frontier markets by MSCI, and are generally located in the AsiaPacific region, Eastern Europe, the Middle East, Central and South America and Africa. There are no geographic limits on the Fund’s non-U.S. investments.
The Fund may invest in companies of any size. but primarily invests in mid-and large-capitalization companies and targeting a balanced allocation across this market capitalization spectrum. At times the Fund may increase the relative emphasis of its investments in a particular region, country, sector, industry or other segment of the market.
The Fund primarily invests in equity securities, including common stocks, preferred stocks, warrants and other rights, and securities convertible into or exchangeable for common stocks. The Fund may also invest in real estate investment trusts (“REITs”), depositary receipts, including American, European and Global Depositary Receipts. The Fund’s investments may be hedged or unhedged to foreign currencies depending on the market opportunities.
The adviser uses a fundamental, bottom up approach to identify what it believes are quality companies, as evidenced by the durability of the company’s business model (strong competitive advantages and high barriers to entry), the company’s financial strength (greater returns on capital, free cash flow generation, healthy balance sheets), the presence of long-term growth, and value-accretive management teams.
From time to time the Fund may invest in companies that are experiencing unusual and possibly unique developments. Potential investments in the stock of these companies are usually the result of companies uncovered in the research process that are otherwise outside of the standard investment criteria employed by the Fund, but may have opportunities for significant returns. These companies are deemed “special situations”. Special situations include companies going through reorganizations, recapitalizations, mergers, spin-offs, or facing resolutions of litigation, management team changes, or important technological improvements or discoveries.
The Fund will buy such quality companies when the adviser believes their fundamentals are mispriced relative to their long-term potential and when their stock prices reflect reasonable valuations.
The Fund will sell companies when fundamentals deteriorate, thus impairing the long-term quality of the business; when the market price exceeds the adviser’s estimate of intrinsic value; when the adviser’s investment thesis supporting its decision to purchase and hold the company is no longer valid; and/or when the adviser believes a more attractive risk/reward opportunity exists.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment
program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Foreign Investing Risk — Foreign securities may underperform U.S. securities and may be more volatile than U.S. securities. Risks relating to investments in foreign securities (including, but not limited to, depositary receipts and participation certificates) and to securities of issuers with significant exposure to foreign markets include currency exchange rate fluctuation; less available public information about the issuers of securities; less stringent regulatory standards; lack of uniform accounting, auditing and financial reporting standards; imposition of foreign withholding and other taxes; country risks, including less liquidity, high inflation rates and unfavorable economic practices; and political instability and expropriation and nationalization risks.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Emerging Markets Risk — Investment risks typically are greater in emerging and less developed markets. For example, in addition to the risks associated with investments in any foreign country, political, legal and economic structures in these less developed countries may be new and changing rapidly, which may cause instability and greater risk of loss. Emerging markets may be less developed, and securities in emerging markets are generally more volatile and less liquid than those in the developed markets. Investing in emerging market countries may involve substantial risk due to, among other reasons, limited issuer information; higher brokerage costs; different and less stringent accounting, auditing and financial reporting standards; less developed legal systems and thinner trading markets as compared to those in developed countries; different clearing and settlement procedures and custodial services; and currency blockages or transfer restrictions. Emerging market countries also are more likely to experience high levels of inflation, deflation or currency devaluations, which could hurt their economies and securities markets. Certain emerging markets also may face other significant internal or external risks, including a heightened risk of war or ethnic, religious or racial conflicts. In addition, governments in many emerging market countries participate to a significant degree in their economies and securities markets, which may impair investment and economic growth of companies in those markets. Such markets may also be heavily reliant on foreign capital and, therefore, vulnerable to capital flight.
•Depositary Receipts Risk — The Fund’s investments in depositary receipts include American Depositary Receipts (“ADRs”), Global Depositary Receipts (“GDRs”) and European Depositary Receipts (“EDRs”). ADRs are receipts issued by U.S. banks evidencing ownership in securities of foreign issuers, and GDRs and EDRs are receipts issued by banks in more than one country evidencing ownership in securities of foreign issuers. Although depositary receipts have risks similar to the foreign securities that they represent, they may also involve higher expenses and may trade at a discount (or premium) to the underlying security. In addition, depositary receipts may not pass through voting and other shareholder rights, and may be less liquid than the underlying securities listed on an exchange.
•Currency Risk — Foreign securities usually are denominated and traded in foreign currencies and the exchange rates between foreign currencies and the U.S. dollar fluctuate continuously. The Fund’s performance will be affected by its direct or indirect exposure, which may include exposure through U.S. dollar denominated depositary receipts and participation certificates, to a particular currency due to favorable or unfavorable changes in currency exchange rates relative to the U.S. dollar. The Fund’s direct or indirect exposure to a particular currency may be hedged to mitigate currency volatility or because the Fund believes a currency is overvalued. There can be no guarantee that any hedging activity will be successful. Hedging activity and/or use of forward foreign currency exchange contracts may reduce or limit the opportunity for gain and involves counterparty risk,
which is the risk that the contracting party will not fulfill its contractual obligation to deliver the currency contracted for at the agreed upon price to the Fund.
•REIT Risk — The Fund’s investments in real estate related securities (primarily REITs) are subject to the risk that the value of the real estate underlying the securities will go down, which can be caused by deteriorating economic conditions and rising interest rates, and may also be subject to the risk that borrowers or tenants may default on their payment obligations. Investments in REITs involve additional risks. REITs may have limited financial resources and real estate diversification and are dependent on specialized management skills. In addition, the failure of a REIT to qualify as a REIT for federal income tax purposes would adversely affect the REIT’s value.
•Large-Cap Companies Risk —Larger, more established companies may be unable to respond quickly to new competitive challenges, such as changes in consumer tastes or innovative smaller competitors. Also, large-cap companies are sometimes unable to attain the high growth rates of successful, smaller companies, especially during extended periods of economic expansion.
•Mid-Cap Companies Risk — The Fund may invest in the securities of companies with mid-capitalizations, which can involve greater risk and the possibility of greater portfolio volatility than investments in securities of large-capitalization companies. Historically, stocks of mid-capitalization companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such stocks. Mid-capitalization companies may have limited product lines and financial resources and may depend upon a limited or less experienced management group.
•Liquidity Risk — Liquidity risk exists when particular investments are difficult to sell, and such investments (particularly investments deemed to be illiquid) may be harder to value. If the Fund sells these investments to meet shareholder redemption requests or for other purposes, the Fund may suffer a loss.
•Region, Country, Sector or Industry Focus Risk — The prices of securities of issuers in a particular region, country, sector, industry or other segment of the market may be more susceptible to fluctuations due to changes in economic or business conditions, government regulations, availability of basic resources or supplies, or other events that affect that market segment more than securities of issuers in other market segments, and such volatility will cause fluctuations in the Fund’s share price to the extent that the Fund emphasizes its investments in that region, county, sector, industry or other market segment.
•Special Situations Risk — The Fund will seek to benefit from “special situations,” such as mergers, reorganizations, or other unusual events expected to affect a particular issuer. There is a risk that the “special situation” might not occur or involve longer time frames than originally expected, which could have a negative impact on the price of the issuer’s securities and fail to produce gains or produce a loss for the Fund.
Risk Lose Money [Text] rr_RiskLoseMoney The Fund’s share price fluctuates, which means you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1 year and since inception compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1 year and since inception compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB International Fund – Return for Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter: 15.55% in the 4th Quarter of 2020
Worst Quarter: -21.52% in the 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, such as 401(k) plans or IRAs.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or IRAs. No returns are provided for Investor Class shares, which have not been offered for sale.
RMB International Fund | MSCI EAFE Index (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel MSCI EAFE Index(reflects no deduction of fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 11.26%
Since Inception rr_AverageAnnualReturnSinceInception 6.10% [6]
RMB International Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.16% [7]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.16%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 118
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 368
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 638
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,409
RMB International Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBTX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.16%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.91%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 93
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 290
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 504
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,120
Annual Return 2018 rr_AnnualReturn2018 (21.81%)
Annual Return 2019 rr_AnnualReturn2019 19.20%
Annual Return 2020 rr_AnnualReturn2020 7.01%
Annual Return 2021 rr_AnnualReturn2021 9.53%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.55%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.52%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 9.53%
Since Inception rr_AverageAnnualReturnSinceInception 2.25% [6]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 27, 2017
RMB International Fund | Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 9.37%
Since Inception rr_AverageAnnualReturnSinceInception 2.19% [6]
RMB International Fund | Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 5.94%
Since Inception rr_AverageAnnualReturnSinceInception 1.83% [6]
RMB Japan Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB Japan Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB Japan Fund (the “Fund”) seeks long-term capital appreciation. There can be no assurance that the Fund will be successful in achieving its investment objective.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 Fee Table or the Example below.
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 April 30, 2023
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays 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 18% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 18.00%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The 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 assumes that you invest $10,000 in the 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 Fund’s operating expenses remain the same, taking into account the Expense Cap in the first year only.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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
The Fund pursues its investment objective by investing, under normal conditions, at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of Japanese companies.
The Adviser considers a Japanese company to be a company organized under the laws of Japan, for which the principal securities trading market is Japan, or a company that has a majority of its assets or business in Japan.
The Fund primarily invests in equity securities, including common stocks, preferred stocks, warrants and other rights and securities convertible into or exchangeable for common stocks. The Fund may also invest in real estate investment trusts (“REITs”) and depositary receipts, including American, European and Global Depositary Receipts. The Fund’s investments may be hedged or unhedged to foreign currencies depending on the market opportunities. The Fund may invest in companies of any size, but primarily invests in mid- and large-capitalization companies and targeting a balanced allocation across this market capitalization spectrum.
The Adviser uses a fundamental, bottom-up research approach. Fundamental analysis includes evaluation of management teams and shareholder structure, and examination of competitive positioning and industry dynamics, including pricing power, stable free cash flow, and barriers to entry.
The Fund will seek to buy companies when the Adviser believes the companies have a sustainable competitive advantage, strong free cash flow and reasonable valuations relative to their long-term potential. The Fund will sell securities when they are no longer trading below their intrinsic value; when the Adviser believes there has been a deterioration in the company’s fundamentals, and/or a change in the company’s business outlook; or when a better use of capital presents itself.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Foreign Investing Risk — Foreign securities may underperform U.S. securities and may be more volatile than U.S. securities. Risks relating to investments in foreign securities (including, but not limited to, depositary receipts and participation certificates) and to securities of issuers with significant exposure to foreign markets include currency exchange rate fluctuation; less available public information about the issuers of securities; less stringent regulatory standards; lack of uniform accounting, auditing and financial reporting standards; imposition of foreign withholding and other taxes; country risks, including less liquidity, high inflation rates and unfavorable economic practices; and political instability and expropriation and nationalization risks.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Risks Associated with Japan — The Japanese economy continues to emerge from a prolonged economic downturn. Since the year 2000, Japan’s economic growth rate has remained relatively low. The economy is characterized by an aging demographic, declining population, large government debt and highly regulated labor market. Economic growth is dependent on domestic consumption, deregulation and consistent government policy. International trade, particularly with the U.S., also impacts growth and adverse economic conditions in the U.S. or other such trade partners may affect Japan. Japan also has a growing economic relationship with China and other Southeast Asian countries, and thus Japan’s economy may also be affected by economic, political, or social instability in those countries (whether resulting from local or global events).
•Currency Risk — Foreign securities usually are denominated and traded in foreign currencies and the exchange rates between foreign currencies and the U.S. dollar fluctuate continuously. The Fund’s performance will be affected by its direct or indirect exposure, which may include exposure through U.S. dollar denominated depositary receipts and participation certificates, to a particular currency due to favorable or unfavorable changes in currency exchange rates relative to the U.S. dollar. The Fund’s direct or indirect exposure to a particular currency may be hedged to mitigate currency volatility or because the Fund believes a currency is overvalued. There can be no guarantee that any hedging activity will be successful. Hedging activity and/or use of forward foreign currency exchange contracts may reduce or limit the opportunity for gain and involves counterparty risk, which is the risk that the contracting party will not fulfill its contractual obligation to deliver the currency contracted for at the agreed upon price to the Fund.
•REIT Risk — The Fund’s investments in real estate related securities (primarily REITs) are subject to the risk that the value of the real estate underlying the securities will go down, which can be caused by deteriorating economic conditions and rising interest rates, and may also be subject to the risk that borrowers or tenants may default on their payment obligations. Investments in REITs involve additional risks. REITs may have limited financial resources and real estate diversification and are dependent on specialized management skills. In addition, the failure of a REIT to qualify as a REIT for federal income tax purposes would adversely affect the REIT’s value.
•Depositary Receipts Risk — The Fund’s investments in depositary receipts include American Depositary Receipts (“ADRs”), Global Depositary Receipts (“GDRs”) and European Depositary Receipts (“EDRs”). ADRs are receipts issued by U.S. banks evidencing ownership in securities of foreign issuers, and GDRs and EDRs are receipts issued by banks in more than one country evidencing ownership in securities of foreign issuers. Although depositary receipts have risks similar to the foreign securities that they represent, they may also involve higher expenses and may trade at a discount (or premium) to the underlying security. In addition, depositary receipts may not pass through voting and other shareholder rights, and may be less liquid than the underlying securities listed on an exchange.
•Large-Cap Companies Risk — Larger, more established companies may be unable to respond quickly to new competitive challenges, such as changes in consumer tastes or innovative smaller competitors. Also, large-cap companies are sometimes unable to attain the high growth rates of successful, smaller companies, especially during extended periods of economic expansion.
•Mid-Cap Companies Risk — The Fund may invest in the securities of companies with mid-capitalizations, which can involve greater risk and the possibility of greater portfolio volatility than investments in securities of large-capitalization companies. Historically, stocks of mid-capitalization companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such stocks. Mid-capitalization companies may have limited product lines and financial resources and may depend upon a limited or less experienced management group.
•Liquidity Risk — Liquidity risk exists when particular investments are difficult to sell, and such investments (particularly investments deemed to be illiquid) may be harder to value. If the Fund sells these investments to meet shareholder redemption requests or for other purposes, the Fund may suffer a loss.
Risk Lose Money [Text] rr_RiskLoseMoney The Fund’s share price fluctuates, which means you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1 year and since inception compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1 year and since inception compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB Japan Fund – Return for Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock Best Quarter: 14.90% in the 4th Quarter of 2020Worst Quarter: -18.84% in the 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, such as 401(k) plans or IRAs.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The “Total Return After Taxes on Distributions and Sale of Fund Shares” can be higher than other return figures when a capital loss occurs upon the redemption of Fund shares. If realized losses occur upon the sale of Fund shares, the capital loss is recorded as a tax benefit, which increases the return.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or IRAs. No returns are provided for Investor Class shares, which have not been offered for sale.
RMB Japan Fund | MSCI Japan Index (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel MSCI Japan Index(reflects no deduction of fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 1.71%
Since Inception rr_AverageAnnualReturnSinceInception 4.91% [8]
RMB Japan Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.48% [9]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.63%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 158
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 506
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 879
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,926
RMB Japan Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBPX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.48%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.38%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.08%) [10]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.30%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 132
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 429
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 748
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,650
Annual Return 2018 rr_AnnualReturn2018 (13.57%)
Annual Return 2019 rr_AnnualReturn2019 17.63%
Annual Return 2020 rr_AnnualReturn2020 13.06%
Annual Return 2021 rr_AnnualReturn2021 (2.56%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 14.90%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (18.84%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (2.56%)
Since Inception rr_AverageAnnualReturnSinceInception 2.77% [8]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 27, 2017
RMB Japan Fund | Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (4.12%)
Since Inception rr_AverageAnnualReturnSinceInception 2.35% [8]
RMB Japan Fund | Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares2 [11]
1 Year rr_AverageAnnualReturnYear01 (0.09%) [11]
Since Inception rr_AverageAnnualReturnSinceInception 2.27% [8],[11]
RMB Small Cap Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB Small Cap Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB Small Cap Fund (the “Fund”) seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 Fee Table or the Example below.
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 April 30, 2023
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays 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 7% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 7.00%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The 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 assumes that you invest $10,000 in the 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 Fund’s operating expenses remain the same, taking into account the Expense Cap in the first year only.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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
The Fund seeks to achieve its investment objective by investing, under normal market conditions, at least 80% of its net assets (plus borrowings for investment purposes) in equity securities of U.S. companies with small market capitalizations. For this purpose, the Adviser defines a small-capitalization company as any company with a market capitalization less than or equal to the largest market capitalization (determined at the time of investment) of any company in the Russell 2000® Index, which, as of March 31, 2022, was approximately $14.86 billion. Equity securities in which the Fund invests consist primarily of common stocks, and may include other types of equity securities. The Fund may also invest in real estate investment trusts (“REITs”).
The Adviser actively manages the Fund by applying an economic return framework that seeks to identify attractively-priced companies at all stages of the corporate lifecycle that allocate capital in a way that creates long-term value. The Adviser’s economic return framework analyzes key determinants of success, such as cash flow, capital investments, credit worthiness and sales momentum. Taking into account a company’s stage in the corporate lifecycle, the Adviser evaluates the sustainability of the company’s economic returns and further evaluates potential investments to determine which stocks are most attractively priced. In managing the Fund, the Adviser seeks to construct a portfolio that is diversified across both economic sectors and corporate lifecycle. As a result of its lifecycle diversification, the Fund invests in both growth- and value-style equity securities.
The Adviser reduces positions or sells securities in the Fund for a variety of reasons, such as when the securities reach their target price or when a position would exceed 5% of the Fund’s net assets.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Small-Cap Companies Risk — Historically, stocks of small-capitalization companies and recently organized companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such securities, which may make these securities difficult to value and to sell. As a result, some of the Fund’s small cap holdings may be considered or become illiquid. Such companies also may have limited product lines and financial resources and may depend upon a limited or less experienced management group.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Growth Investing Risk — Growth companies are generally more susceptible than established companies to market events and sharp declines in value.
•Value Investing Risk — Value stocks may not increase in price, may not issue the anticipated stock dividends or may decline in price, based upon the market’s belief of the issuer’s intrinsic worth.
•REIT Risk — The Fund’s investments in real estate related securities (primarily REITs) are subject to the risk that the value of the real estate underlying the securities will go down, which can be caused by deteriorating economic conditions and rising interest rates, and may also be subject to the risk that borrowers or tenants may default on their payment obligations. Investments in REITs involve additional risks. REITs may have limited financial resources and real estate diversification and are dependent on specialized management skills. In addition, the failure of a REIT to qualify as a REIT for federal income tax purposes would adversely affect the REIT’s value.
Risk Lose Money [Text] rr_RiskLoseMoney The Fund’s share price fluctuates, which means you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5, and 10 years compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.The Fund commenced operations upon completion of the reorganization of the IronBridge Small Cap Fund (the “IronBridge Predecessor Fund”), a series of IronBridge Funds, Inc., into the Fund, which occurred on June 21, 2019 (the “IronBridge Reorganization”). As a result of the IronBridge Reorganization, the performance and accounting history of the IronBridge Predecessor Fund were assumed by the Fund’s Class I shares. Prior to June 21, 2019, the Fund’s Class I performance shown is that of the IronBridge Predecessor Fund.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5, and 10 years compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB Small Cap Fund – Return for Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter: 28.97% in the 4th Quarter of 2020
Worst Quarter: -26.83% in the 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, such as 401(k) plans or IRAs.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or IRAs. No returns are provided for Investor Class shares, which have not been offered for sale.
RMB Small Cap Fund | Russell 2000 Index (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 2000® Index(reflects no deduction of fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 14.82%
5 Years rr_AverageAnnualReturnYear05 12.02%
10 Years rr_AverageAnnualReturnYear10 13.23%
RMB Small Cap Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21% [12]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.31%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.11%) [13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.20%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 122
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 404
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 708
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,569
RMB Small Cap Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBBX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.85%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.21%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.06%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.11%) [13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.95%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 97
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 326
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 574
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,284
Annual Return 2011 rr_AnnualReturn2011 (3.79%)
Annual Return 2012 rr_AnnualReturn2012 13.20%
Annual Return 2013 rr_AnnualReturn2013 33.26%
Annual Return 2014 rr_AnnualReturn2014 6.16%
Annual Return 2015 rr_AnnualReturn2015 (1.97%)
Annual Return 2016 rr_AnnualReturn2016 13.70%
Annual Return 2017 rr_AnnualReturn2017 10.43%
Annual Return 2018 rr_AnnualReturn2018 (4.97%)
Annual Return 2019 rr_AnnualReturn2019 27.47%
Annual Return 2020 rr_AnnualReturn2020 17.59%
Annual Return 2021 rr_AnnualReturn2021 24.38%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 28.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.83%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 24.38%
5 Years rr_AverageAnnualReturnYear05 14.37%
10 Years rr_AverageAnnualReturnYear10 13.32%
RMB Small Cap Fund | Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 22.54%
5 Years rr_AverageAnnualReturnYear05 10.89%
10 Years rr_AverageAnnualReturnYear10 10.52%
RMB Small Cap Fund | Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 15.68%
5 Years rr_AverageAnnualReturnYear05 10.50%
10 Years rr_AverageAnnualReturnYear10 10.18%
RMB SMID Cap Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading RMB SMID Cap Fund
Objective [Heading] rr_ObjectiveHeading INVESTMENT OBJECTIVE:
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The RMB SMID Cap Fund (the “Fund”) seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading FEES AND EXPENSES OF THE FUND
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The table below describes the fees and expenses 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 Fee Table or the Example below.
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 April 30, 2023
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading PORTFOLIO TURNOVER
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The Fund pays 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 9% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 9.00%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The 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 assumes that you invest $10,000 in the 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 Fund’s operating expenses remain the same, taking into account the Expense Cap in the first year only.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption 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
The Fund seeks to achieve its investment objective by investing, under normal market conditions, at least 80% of its net assets (plus borrowings for investment purposes) in equity securities of companies with small- to-mid- market capitalizations.  For this purpose, the Adviser defines a small- to-mid- capitalization company as a company that has a market capitalization of between $500 million and $40.02 billion at the time of purchase. Equity securities in which the Fund invests consist primarily of common stocks, and may include other types of equity securities. The Fund may also invest in real estate investment trusts (“REITs”).
The Adviser actively manages the Fund by applying an economic return framework that seeks to identify attractively-priced companies at all stages of the corporate lifecycle that allocate capital in a way that creates long-term value. The Adviser’s economic return framework analyzes key determinants of success, such as cash flow, capital investments, credit worthiness and sales momentum. Taking into account a company’s stage in the corporate lifecycle, the Adviser evaluates the sustainability of the company’s economic returns and further evaluates potential investments to determine which stocks are most attractively priced. In managing the Fund, the Adviser seeks to construct a portfolio that is diversified across both economic sectors and corporate lifecycle. As a result of its lifecycle diversification, the Fund invests in both growth- and value-style equity securities.
The Adviser reduces positions or sells securities in the Fund for a variety of reasons, such as when the securities reach their target price or when a position would exceed 5% of the Fund’s net assets.
Risk [Heading] rr_RiskHeading PRINCIPAL RISKS
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any mutual fund, there is no guarantee that the Fund will achieve its objective. The Fund’s share price fluctuates, which means you could lose money by investing in the Fund. The Fund is not a complete investment program and should be considered only as part of an investment portfolio. The principal risks of investing in the Fund are summarized below:
•Market Risk — This is the risk that the price of a security will fall due to changing economic, political or market conditions, or due to a company’s individual situation. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The risk would be greater if any of the categories of securities that the Fund emphasizes fell out of favor with the market. Companies in the Fund’s portfolio could fail to achieve earnings estimates or other market expectations, causing their stock prices to drop.
•Equity Securities Risk — The risk that the market price of common stocks and other equity securities, including preferred stocks, warrants and rights, may go up or down, sometimes rapidly or unpredictably, including due to factors affecting equity securities markets generally, particular industries represented in those markets, or the issuer itself.
•Management Risk — The Fund is subject to management risk because it is an actively managed investment portfolio. The adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its decisions will produce the intended result. The Fund’s management strategy or security selection methods could prove less successful than anticipated or unsuccessful. This risk is common for all actively managed funds. Individual stocks selected by the adviser may decline in value or not increase in value, even when the stock market in general is rising.
•Small- and Mid-Cap Companies Risk — The Fund may invest in the securities of companies with small- and mid-capitalizations, which can involve greater risk and the possibility of greater portfolio volatility than investments in securities of large- capitalization companies. Historically, stocks of small- and mid-capitalization companies and recently organized companies have been more volatile in price than those of the larger market capitalization companies. Among the reasons for the greater price volatility is the lower degree of liquidity in the markets for such stocks. Small- and mid-capitalization companies may have limited product lines and financial resources and may depend upon a limited or less experienced management group. The securities of small-capitalization companies trade in the over-the-counter markets or on regional exchanges and may not be traded daily or in the volume typical of trading on a national securities exchange, which may make these securities more difficult to value and to sell.
•Growth Investing Risk — Growth companies are generally more susceptible than established companies to market events and sharp declines in value.
•Value Investing Risk — Value stocks may not increase in price, may not issue the anticipated stock dividends or may decline in price, based upon the market’s belief of the issuer’s intrinsic worth.
•REIT Risk — The Fund’s investments in real estate related securities (primarily REITs) are subject to the risk that the value of the real estate underlying the securities will go down, which can be caused by deteriorating economic conditions and rising interest rates, and may also be subject to the risk that borrowers or tenants may default on their payment obligations. Investments in REITs involve additional risks. REITs may have limited financial resources and real estate diversification and are dependent on specialized management skills. In addition, the failure of a REIT to qualify as a REIT for federal income tax purposes would adversely affect the REIT’s value.
•Large Shareholder Risk — From time to time, shareholders of the Fund may make relatively large redemptions or purchases of Fund shares. These transactions may cause the Fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the Fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the Fund’s performance to the extent that it takes time to invest new cash and the Fund maintains a larger cash position than it ordinarily would.
Risk Lose Money [Text] rr_RiskLoseMoney The Fund’s share price fluctuates, which means you could lose money by investing in the Fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading PAST PERFORMANCE
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5, and 10 years compare with those of a broad measure of market performance. The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses. Bear in mind that past performance (before and after taxes) is not a guarantee of future performance. Updated performance information may be obtained on the Fund’s website at www.rmbfunds.com or by calling 1-800-462-2392.The Fund commenced operations upon completion of the reorganization of the IronBridge SMID Cap Fund (the “IronBridge Predecessor Fund”), a series of IronBridge Funds, Inc., into the Fund, which occurred on June 21, 2019 (the “IronBridge Reorganization”). As a result of the IronBridge Reorganization, the performance and accounting history of the IronBridge Predecessor Fund were assumed by the Fund’s Class I shares. Prior to June 21, 2019, the performance shown is that of the IronBridge Predecessor Fund, which commenced operations on July 23, 2010.
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 Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual total returns for 1, 5, and 10 years compare with those of a broad measure of market performance.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-462-2392
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.rmbfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Bear in mind that past performance (before and after taxes) is not a guarantee of future performance.
Bar Chart [Heading] rr_BarChartHeading RMB SMID Cap Fund – Return for Class I Shares
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter:25.40% in the 2nd Quarter of 2020
Worst Quarter: -25.28% in the 1st Quarter of 2020
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns (For the following periods ended 12/31/2021)
Performance Table Does Reflect Sales Loads rr_PerformanceTableDoesReflectSalesLoads The Fund’s performance figures assume that all distributions were reinvested in the Fund and reflect the Fund’s operating expenses.
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction of fees, expenses or taxes)
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 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-advantaged arrangements, such as 401(k) plans or IRAs.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock 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-advantaged arrangements, such as 401(k) plans or IRAs. No returns are provided for Investor Class shares, which have not been offered for sale.
RMB SMID Cap Fund | Russell 2500TM Index (reflects no deduction of fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 2500TM Index(reflects no deduction of fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 18.18%
5 Years rr_AverageAnnualReturnYear05 13.75%
10 Years rr_AverageAnnualReturnYear10 14.15%
RMB SMID Cap Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14% [14]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.09%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.05%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 107
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 343
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 597
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,325
RMB SMID Cap Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol RMBMX
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.70%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.84%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.04%) [15]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.80%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 82
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 264
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 462
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,033
Annual Return 2011 rr_AnnualReturn2011 (2.82%)
Annual Return 2012 rr_AnnualReturn2012 12.70%
Annual Return 2013 rr_AnnualReturn2013 31.39%
Annual Return 2014 rr_AnnualReturn2014 3.66%
Annual Return 2015 rr_AnnualReturn2015 (0.87%)
Annual Return 2016 rr_AnnualReturn2016 12.28%
Annual Return 2017 rr_AnnualReturn2017 13.66%
Annual Return 2018 rr_AnnualReturn2018 (4.89%)
Annual Return 2019 rr_AnnualReturn2019 31.63%
Annual Return 2020 rr_AnnualReturn2020 24.39%
Annual Return 2021 rr_AnnualReturn2021 28.10%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.40%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2020
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (25.28%)
Label rr_AverageAnnualReturnLabel Total Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 28.10%
5 Years rr_AverageAnnualReturnYear05 17.79%
10 Years rr_AverageAnnualReturnYear10 14.50%
RMB SMID Cap Fund | Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 26.46%
5 Years rr_AverageAnnualReturnYear05 14.93%
10 Years rr_AverageAnnualReturnYear10 11.78%
RMB SMID Cap Fund | Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Total Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 17.72%
5 Years rr_AverageAnnualReturnYear05 13.47%
10 Years rr_AverageAnnualReturnYear10 11.11%
[1] “Total return” of the index reflects reinvestment of dividends in the index.
[2] Class I shares commenced investment operations on February 1, 2017. Performance shown prior to February 1, 2017 for the Class I shares reflects the performance of Class A shares. Class I shares are not subject to the front-end sales charge or distribution and shareholder service (12b-1) fees applicable to Class A shares, which reduce the performance shown for the Class I shares.
[3] Total return” of the index reflects reinvestment of dividends in the index.
[4] Total Annual Fund Operating Expenses do not correlate to the Ratio of Expenses to Average Net Assets in the Financial Highlights section of the statutory prospectus, which reflects the operating expenses of the Fund and does not include acquired fund fees and expenses (“AFFE”).
[5] Class I shares commenced investment operations on February 1, 2017. Performance shown prior to February 1, 2017 for the Class I shares reflects the performance of Class A shares. Class I shares are not subject to the front-end sales charge or distribution and shareholder service (12b-1) fees applicable to Class A shares, which reduce the performance shown for the Class I shares.
[6] Class I shares commenced investment operations on December 27, 2017.
[7] Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
[8] Class I shares commenced investment operations on December 27, 2017.2The “Total Return After Taxes on Distributions and Sale of Fund Shares” can be higher than other return figures when a capital loss occurs upon the redemption of Fund shares. If realized losses occur upon the sale of Fund shares, the capital loss is recorded as a tax benefit, which increases the return.
[9] Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
[10] RMB Capital Management, LLC (the “Adviser”) has contractually agreed to reduce its compensation due from and/or assume expenses of the Fund to the extent necessary to ensure that the Fund’s operating expenses (excluding interest, taxes, brokerage commissions and other transaction costs, expenditures that are capitalized in accordance with generally accepted accounting principles, acquired fund fees and expenses, short sale dividends and extraordinary expenses not incurred in the ordinary course of business) do not exceed 1.55% and 1.30% of the average daily net assets of the Fund’s Investor Class and Class I shares, respectively (the “Expense Cap”). The Expense Cap is in effect through April 30, 2023 and cannot be terminated prior thereto without the approval of the Fund’s Board of Trustees. To the extent the Adviser waives its compensation and/or assumes expenses to satisfy the Expense Cap, the Adviser may seek repayment by the Fund of a portion or all of such amounts at any time within three years from the date on which such amounts were waived or assumed, provided that the Fund is able to make the repayment without exceeding the lesser of the expense cap in effect at the time of the waiver/reimbursement or in effect at the time of the repayment.
[11] The “Total Return After Taxes on Distributions and Sale of Fund Shares” can be higher than other return figures when a capital loss occurs upon the redemption of Fund shares. If realized losses occur upon the sale of Fund shares, the capital loss is recorded as a tax benefit, which increases the return.
[12] Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
[13] RMB Capital Management, LLC (the “Adviser”) has contractually agreed to reduce its compensation due from and/or assume expenses of the Fund to the extent necessary to ensure that the Fund’s operating expenses (excluding, interest, taxes, brokerage commissions and other transaction costs, expenditures that are capitalized in accordance with generally accepted accounting principles, acquired fund fees and expenses, if any, and other extraordinary expenses not incurred in the ordinary course of business) do not exceed 1.20% and 0.95% of the average net assets of the Fund’s Investor Class and Class I, respectively (the “Expense Cap”). The Expense Cap is in effect through April 30, 2023 and cannot be terminated prior thereto without the approval of the Fund’s Board of Trustees. To the extent the Adviser waives its compensation and/or assumes expenses to satisfy the Expense Cap, the Adviser may seek repayment by the Fund of a portion or all of such amounts at any time within three years from the date on which such amounts were waived or assumed, provided that the Fund is able to make the repayment without exceeding the lesser of the expense cap in effect at the time of the waiver/reimbursement of in effect at the time of the repayment.
[14] Investor Class shares of the Fund are not currently offered for purchase. As a result, “Other Expenses” for Investor Class shares have been estimated.
[15] RMB Capital Management, LLC (the “Adviser”) has contractually agreed to reduce its compensation due from and/or assume expenses of the Fund to the extent necessary to ensure that the Fund’s operating expenses (excluding interest, taxes, brokerage commissions and other transaction costs, expenditures that are capitalized in accordance with generally accepted accounting principles and acquired fund fees and expenses, if any, and other extraordinary expenses not incurred in the ordinary course of business) do not exceed 1.05% and 0.80% of the average net assets of the Fund’s Investor Class and Class I, respectively (the “Expense Cap”). The Expense Cap is in effect through April 30, 2023 and cannot be terminated prior thereto without the approval of the Fund’s Board of Trustees. To the extent the Adviser waives its compensation and/or assumes expenses to satisfy the Expense Cap, the Adviser may seek repayment by the Fund of a portion or all of such amounts at any time within three years from the date on which such amounts were waived or assumed, provided that the Fund is able to make the repayment without exceeding the lesser of the expense cap in effect at the time of the waiver/reimbursement or in effect at the time of the repayment.