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Jacob Forward ETF  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading JACOB FORWARD ETF
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Jacob Forward ETF (the “Fund”) seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses you may pay if you buy, hold, and sell shares of the Fund (“Shares”). You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and the Example below.
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 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. For the fiscal year ended August 31, 2023, the Fund’s portfolio turnover rate was 63% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 63.00%
Expense Example [Heading] rr_ExpenseExampleHeading Expense Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell or hold 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. The Example does not take into account brokerage commissions that you may pay on your purchases and sales of Shares.
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 Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund seeks to achieve its investment objective by investing in common stocks and other equity securities of companies of all sizes. The Fund maintains a portfolio of investments consisting primarily of common stocks. The Fund may also invest in other equity securities, such as preferred stocks, rights, or warrants. The Fund may have significant exposure to the health care and information technology sectors.
The Fund is managed utilizing a forward-looking investment strategy and seeks to invest in companies that are participating or engaged in innovative and disruptive technologies, products, or services. The Fund invests in a broad group of companies, including many that are in their early stages of development. In researching and selecting investments for the Fund, the Adviser is seeking strong, forward-looking management teams that can leverage innovative technology to obtain durable competitive advantages in order to generate superior rates of growth. The Adviser’s overall stock selections are based on its qualitative and quantitative assessment of a company’s fundamental prospects, particularly a company’s potential for superior long-term growth of capital. It is the Adviser’s goal to maximize the growth potential of the Fund while also striving to acquire securities at reasonable valuations relative to their prospective growth rates.
The Adviser expects to invest the Fund’s net assets primarily in U.S. companies, but may gain exposure to foreign markets, including emerging markets, (i.e., those that are in the early stages of their industrial cycles), through the global operations of U.S. companies, by purchasing depositary receipts or securities of foreign companies traded on U.S. exchanges, or through direct investment in foreign companies. The Adviser currently does not expect to invest more than 25% of the Fund’s net assets directly in foreign companies.
The Fund is considered to be non-diversified, which means that it may invest more of its assets in the securities of a single issuer or smaller number of issuers than if it were a diversified fund.
The Fund may lend its portfolio securities to see to generate additional income.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The performance information that follows gives some indication of the risks of investing in the Fund. The bar chart shows the Fund’s performance from year to year, and the table compares the Fund’s average annual returns with those of a broad measure of market performance for the most recent calendar year. Please note that the Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Updated performance information is available on the Fund’s website at www.jacobforwardetf.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The performance information that follows gives some indication of the risks of investing in the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.jacobforwardetf.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Please note that the Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Annual Total Returns through December 31, 2022
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter
Q3 2022
5.10%
Worst Quarter
Q2 2022
-41.69%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2022
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 5.10%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (41.69%)
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns through December 31, 2022
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes (reflects no deduction for 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.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
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. The return after taxes on distribution and sale of fund shares may be higher than the return before taxes because the method of calculation assumes generally that you can use the short-term capital loss realized upon the sale of fund shares to offset income of the same tax character from other sources thereby reducing the amount of tax you otherwise might owe.
Jacob Forward ETF | Risk Nondiversified Status [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Non-Diversification Risk: The Fund is considered to be non-diversified, which means that it may invest more of its assets in the securities of a single issuer or a smaller number of issuers than if it were a diversified fund. As a result, the Fund may be more exposed to the risks associated with and developments affecting an individual issuer or a smaller number of issuers than a fund that invests more widely. This may increase the Fund’s volatility and cause the performance of a relatively smaller number of issuers to have a greater impact on the Fund’s performance.
Jacob Forward ETF | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock As with any investment, there is a risk that you could lose all or a portion of your investment in the Fund.
Jacob Forward ETF | Growth Companies Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Growth Companies Risk: Growth companies are expected to increase their earnings at a certain rate. When these expectations are not met, the prices of these stocks may go down, even if earnings showed an absolute increase. Growth company stocks also typically lack the dividend yield that can cushion stock prices in market downturns. Different investment styles tend to shift in and out of favor, depending on market conditions and investor sentiment. The Fund’s growth style may cause the Fund to underperform funds that have a broader investment style.
Jacob Forward ETF | Sector Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Sector Risk: Sector risk is the possibility that securities within the same group of industries will decline in price due to sector-specific market or economic developments. If the Fund invests more heavily in a particular sector, the value of its shares may be especially sensitive to factors and economic risks that specifically affect that sector. As a result, the Fund’s share price may fluctuate more widely than the value of shares of a fund that invests in a broader range of industries.
◦Healthcare Sector Risk: To the extent the Fund focuses on the healthcare sector, the Fund may be more susceptible to the particular risks that may affect companies in the healthcare sector than if it were invested in a wider variety of companies in unrelated sectors. The profitability of companies in the healthcare sector may be adversely affected by the following factors, among others: extensive government regulations, restrictions on government reimbursement for medical expenses, rising costs of medical products and services, pricing pressure, an increased emphasis on outpatient services, changes in the demand for medical products and services, a limited number of products, industry innovation, changes in technologies and other market developments.
◦Information Technology Sector Risk: Market or economic factors impacting information technology companies and companies that rely heavily on technological advances could have a significant effect on the value of the Fund’s investments. The value of stocks of information technology companies and companies that rely heavily on technology is particularly vulnerable to rapid changes in technology product cycles, rapid product obsolescence, government regulation and competition, both domestically and internationally, including competition from foreign competitors with lower production costs.
Jacob Forward ETF | Sector Risk, Healthcare Sector Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Healthcare Sector Risk: To the extent the Fund focuses on the healthcare sector, the Fund may be more susceptible to the particular risks that may affect companies in the healthcare sector than if it were invested in a wider variety of companies in unrelated sectors. The profitability of companies in the healthcare sector may be adversely affected by the following factors, among others: extensive government regulations, restrictions on government reimbursement for medical expenses, rising costs of medical products and services, pricing pressure, an increased emphasis on outpatient services, changes in the demand for medical products and services, a limited number of products, industry innovation, changes in technologies and other market developments.
Jacob Forward ETF | Sector Risk, Information Technology Sector Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Information Technology Sector Risk: Market or economic factors impacting information technology companies and companies that rely heavily on technological advances could have a significant effect on the value of the Fund’s investments. The value of stocks of information technology companies and companies that rely heavily on technology is particularly vulnerable to rapid changes in technology product cycles, rapid product obsolescence, government regulation and competition, both domestically and internationally, including competition from foreign competitors with lower production costs.
Jacob Forward ETF | Common Stock Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Common Stock Risk: Common stock represents an ownership interest in a company. Holders of common stock are generally subject to greater risk than holders of preferred stocks and debt securities because common stockholders generally have inferior rights to receive payments from issuers in comparison with the rights of preferred stockholders, bondholders, and other creditors. Furthermore. common stocks are susceptible to general stock market fluctuations and to volatile increases and decreases in value as market confidence in, and perceptions of, their issuers change.
Jacob Forward ETF | Market Capitalization Risks Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Market Capitalization Risks:
◦Large Capitalized Company Risk: The securities of large-capitalization companies may be relatively mature compared to smaller companies and therefore subject to slower growth during times of economic expansion. Large-capitalization companies may also be unable to respond quickly to new competitive challenges, such as changes in technology and consumer tastes.
◦Mid Capitalized Company Risk: The securities of mid-capitalization companies may be more vulnerable to adverse issuer, market, political, or economic developments than securities of large-capitalization companies. The securities of mid-capitalization companies generally trade in lower volumes and are subject to greater and more unpredictable price changes than large capitalization stocks or the stock market as a whole. Some mid-capitalization companies have limited product lines, markets, financial resources, and management personnel and tend to concentrate on fewer geographical markets relative to large-capitalization companies.
◦Smaller Capitalized or Unseasoned Company Risk: Investments in smaller capitalized or unseasoned companies may involve greater risks, in part because they have limited product lines, markets and financial or managerial resources. In addition, less frequently traded securities may be subject to more abrupt price movements than securities of larger capitalized companies.
◦Micro-Capitalized Company Risk: Investments in micro capitalization companies may involve greater risks, as these companies tend to have limited product lines, markets and financial or managerial resources. Micro cap stocks often also have a more limited trading market, such that the Adviser may not be able to sell stocks at an optimal time or price. In addition, less frequently traded securities may be subject to more abrupt price movements than securities of larger capitalized companies.
Jacob Forward ETF | Market Capitalization Risks, Large Capitalized Company Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Large Capitalized Company Risk: The securities of large-capitalization companies may be relatively mature compared to smaller companies and therefore subject to slower growth during times of economic expansion. Large-capitalization companies may also be unable to respond quickly to new competitive challenges, such as changes in technology and consumer tastes.
Jacob Forward ETF | Market Capitalization Risks, Mid Capitalized Company Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Mid Capitalized Company Risk: The securities of mid-capitalization companies may be more vulnerable to adverse issuer, market, political, or economic developments than securities of large-capitalization companies. The securities of mid-capitalization companies generally trade in lower volumes and are subject to greater and more unpredictable price changes than large capitalization stocks or the stock market as a whole. Some mid-capitalization companies have limited product lines, markets, financial resources, and management personnel and tend to concentrate on fewer geographical markets relative to large-capitalization companies.
Jacob Forward ETF | Market Capitalization Risks, Smaller Capitalized or Unseasoned Company Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Smaller Capitalized or Unseasoned Company Risk: Investments in smaller capitalized or unseasoned companies may involve greater risks, in part because they have limited product lines, markets and financial or managerial resources. In addition, less frequently traded securities may be subject to more abrupt price movements than securities of larger capitalized companies.
Jacob Forward ETF | Market Capitalization Risks, Micro-Capitalized Company Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Micro-Capitalized Company Risk: Investments in micro capitalization companies may involve greater risks, as these companies tend to have limited product lines, markets and financial or managerial resources. Micro cap stocks often also have a more limited trading market, such that the Adviser may not be able to sell stocks at an optimal time or price. In addition, less frequently traded securities may be subject to more abrupt price movements than securities of larger capitalized companies.
Jacob Forward ETF | Market Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Market Risk: The value of the securities in which the Fund invests may be adversely affected by fluctuations in the financial markets, regardless of how well the companies in which the Fund invests perform. The market as a whole may not favor the
types of investments the Fund makes. Also, there is the risk that the price(s) of one or more of the securities or other instruments in the Fund’s portfolio will fall or will fail to rise. Many factors can adversely affect a security’s performance, including both general financial market conditions and factors related to a specific company, government, industry, country, or geographic region. Extraordinary events, including extreme economic or political conditions, natural disasters, epidemics and pandemics, and other factors can lead to volatility in local, regional, or global markets, which can result in market losses that may be substantial. The impact of one of these types of events may be more pronounced in certain regions, sectors, industries, or asset classes in which the Fund invests, or it may be pervasive across the global financial markets. The timing and occurrence of future market disruptions cannot be predicted, nor can the impact that government interventions, if any, adopted in response to such disruptions may have on the investment strategies of the Fund or the markets in which the Fund invests.
Jacob Forward ETF | Recent Market Events Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Recent Market Events Risk: U.S. and international markets have experienced a significant period of volatility in recent months and years due to a number of economic, political and global macro factors, including the impact of the coronavirus (COVID-19) as a global pandemic, which has at times resulted in public health issues, business interruptions, growth concerns in the U.S. and overseas, layoffs, rising unemployment claims, changed travel and social behaviors and reduced consumer spending. The impact of these events and other epidemics or pandemics in the future could adversely affect Fund performance.
Jacob Forward ETF | ETF Risks Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock ETF Risks: The Fund is an ETF, and, as a result of an ETF’s structure, it is exposed to the following risks:
◦Authorized Participants, Market Makers, and Liquidity Providers Concentration Risk: The Fund has a limited number of financial institutions that may act as Authorized Participants (“APs”). In addition, there may be a limited number of market makers and/or liquidity providers in the marketplace. To the extent either of the following events occur, Shares may trade at a material discount to NAV and possibly face delisting: (i) APs exit the business or unwilling or otherwise become unable to process creation and/or redemption orders (either because of valuation difficulties or for other reasons), and no other AP is able or willing to step forward to perform these services, or (ii) market makers and/or liquidity providers exit the business or significantly reduce their business activities and no other entities step forward to perform their functions.
◦Costs of Buying or Selling Shares: Due to the costs of buying or selling Shares, including brokerage commissions imposed by brokers and bid-ask spreads, frequent trading of Shares may significantly reduce investment results and an investment in Shares may not be advisable for investors who anticipate regularly making small investments.
◦Shares May Trade at Prices Other Than NAV: As with all ETFs, Shares may be bought and sold in the secondary market at market prices. Although it is expected that the market price of Shares will approximate the Fund’s NAV, there may be times when the market price of Shares is more than the NAV intra-day (premium) or less than the NAV intra-day (discount), which may be due to supply and demand of Shares or other reasons. This risk is heightened in times of market volatility, periods of steep market declines, and periods when there is limited trading activity for Shares in the secondary market, in which case such premiums or discounts may be significant. If an investor purchases Shares at a time when the market price is at a premium to the NAV of the Shares or sells at a time when the market price is at a discount to the NAV of the Shares, then the investor may sustain losses that are in addition to any losses caused by a decrease in NAV. For example, during a “flash crash,” the market prices of Shares may decline suddenly and significantly. Such a decline may not reflect the performance of the portfolio securities held by the Fund. Flash crashes may cause APs and other market makers to limit or cease trading in Shares for temporary or longer periods. Shareholders could suffer significant losses to the extent that they sell Shares at these temporarily low market prices. To the extent that the Fund holds securities that trade on foreign exchanges that are closed when the Fund’s primary listing exchange is open, the Fund is likely to experience premiums and discounts greater than those of ETFs that hold only domestic securities.
◦Trading: Although Shares are listed for trading on the NYSE Arca, Inc. (the “Exchange”) and may be traded on U.S. exchanges other than the Exchange, there can be no assurance that Shares will trade with any volume, or at all, on any stock exchange. In stressed market conditions, the liquidity of Shares may begin to mirror the liquidity of the Fund’s underlying portfolio holdings, which can be significantly less liquid than Shares.
Jacob Forward ETF | ETF Risks, Authorized Participants Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Authorized Participants, Market Makers, and Liquidity Providers Concentration Risk: The Fund has a limited number of financial institutions that may act as Authorized Participants (“APs”). In addition, there may be a limited number of market makers and/or liquidity providers in the marketplace. To the extent either of the following events occur, Shares may trade at a material discount to NAV and possibly face delisting: (i) APs exit the business or unwilling or otherwise become unable to process creation and/or redemption orders (either because of valuation difficulties or for other reasons), and no other AP is able or willing to step forward to perform these services, or (ii) market makers and/or liquidity providers exit the business or significantly reduce their business activities and no other entities step forward to perform their functions.
Jacob Forward ETF | ETF Risks, Costs Of Buying Or Selling Shares Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Costs of Buying or Selling Shares: Due to the costs of buying or selling Shares, including brokerage commissions imposed by brokers and bid-ask spreads, frequent trading of Shares may significantly reduce investment results and an investment in Shares may not be advisable for investors who anticipate regularly making small investments.
Jacob Forward ETF | ETF Risks, Shares May Trade At Prices Other Than NAV Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Shares May Trade at Prices Other Than NAV: As with all ETFs, Shares may be bought and sold in the secondary market at market prices. Although it is expected that the market price of Shares will approximate the Fund’s NAV, there may be times when the market price of Shares is more than the NAV intra-day (premium) or less than the NAV intra-day (discount), which may be due to supply and demand of Shares or other reasons. This risk is heightened in times of market volatility, periods of steep market declines, and periods when there is limited trading activity for Shares in the secondary market, in which case such premiums or discounts may be significant. If an investor purchases Shares at a time when the market price is at a premium to the NAV of the Shares or sells at a time when the market price is at a discount to the NAV of the Shares, then the investor may sustain losses that are in addition to any losses caused by a decrease in NAV. For example, during a “flash crash,” the market prices of Shares may decline suddenly and significantly. Such a decline may not reflect the performance of the portfolio securities held by the Fund. Flash crashes may cause APs and other market makers to limit or cease trading in Shares for temporary or longer periods. Shareholders could suffer significant losses to the extent that they sell Shares at these temporarily low market prices. To the extent that the Fund holds securities that trade on foreign exchanges that are closed when the Fund’s primary listing exchange is open, the Fund is likely to experience premiums and discounts greater than those of ETFs that hold only domestic securities.
Jacob Forward ETF | ETF Risks, Trading Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Trading: Although Shares are listed for trading on the NYSE Arca, Inc. (the “Exchange”) and may be traded on U.S. exchanges other than the Exchange, there can be no assurance that Shares will trade with any volume, or at all, on any stock exchange. In stressed market conditions, the liquidity of Shares may begin to mirror the liquidity of the Fund’s underlying portfolio holdings, which can be significantly less liquid than Shares.
Jacob Forward ETF | Limited Operating History Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Limited Operating History: The Fund is a recently organized investment company with a limited operating history. As a result, prospective investors have a limited track record or history on which to base their investment decision. The Fund may also experience low trading volume and wide bid/ask spreads and may face the risk of being delisted if the Fund does not meet certain conditions of the Exchange. If the Fund were to be required to delist from the Exchange the value of the Fund may rapidly decline and performance may be negatively impacted. In addition, any resulting liquidation of the Fund could cause the Fund to incur elevated transaction costs for the Fund and negative tax consequences for its shareholders.
Jacob Forward ETF | Foreign And Emerging Market Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Foreign and Emerging Market Risk:  The risks of investing in foreign companies, including those located in emerging market countries, can increase the potential for losses in the Fund and may include currency fluctuations, political and economic instability, less government regulation, less publicly available information, limited trading markets, differences in financial reporting standards, including recordkeeping standards and less stringent regulation of securities markets. Foreign securities markets generally have less volume than U.S. securities exchanges and securities of some foreign companies are less liquid and more volatile than securities of comparable U.S. companies. Additional risks include future political and economic developments, the possibility that a foreign jurisdiction might impose or increase withholding taxes on income payable with respect to foreign securities, the possible seizure, nationalization or expropriation of the foreign issuer or foreign deposits (in which the Fund could lose its entire investment in a certain market) and the possible adoption of foreign governmental restrictions such as exchange controls. These risks are typically greater in emerging markets countries.
Jacob Forward ETF | Management Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Management Risk: Because the Fund is actively managed, an investment in the Fund is subject to the risk that the investment techniques and risk analyses applied by the Adviser will not produce the desired results, and that the Fund’s investments may underperform the market or applicable benchmarks.
Jacob Forward ETF | Geographic Focus Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Geographic Focus Risk. If the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if its investments were not so concentrated in such country or region.
Jacob Forward ETF | Securities Lending Risk Member  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock Securities Lending Risk. When the Fund lends its portfolio securities, the Fund is subject to the risk that the borrower may fail to return the securities in a timely manner or at all, resulting in a loss to the Fund and/or a delay in recovering the loaned securities. The Fund could also lose money in connection with securities lending transactions if it does not recover the loaned securities and/or the value of the collateral falls, including the value of investments made with cash collateral. Securities lending also may have certain adverse tax consequences. The Fund is not obligated to engage in securities lending, and may discontinue its securities lending activities at any time.
Jacob Forward ETF | S&P 500 Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel S&P 500 Index(reflects no deduction for fees, expenses or taxes)
1 Year rr_AverageAnnualReturnYear01 (18.11%)
Since Inception rr_AverageAnnualReturnSinceInception (6.99%)
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 13, 2021
Jacob Forward ETF | Jacob Forward ETF  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol JFWD
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.75% [1]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets none
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 240
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 417
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 930
Annual Return 2022 rr_AnnualReturn2022 (56.40%)
Label rr_AverageAnnualReturnLabel Return Before Taxes
1 Year rr_AverageAnnualReturnYear01 (56.40%)
Since Inception rr_AverageAnnualReturnSinceInception (47.50%)
Inception Date rr_AverageAnnualReturnInceptionDate Jul. 13, 2021
Jacob Forward ETF | Jacob Forward ETF | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
1 Year rr_AverageAnnualReturnYear01 (56.40%)
Since Inception rr_AverageAnnualReturnSinceInception (47.55%)
Jacob Forward ETF | Jacob Forward ETF | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
1 Year rr_AverageAnnualReturnYear01 (33.39%)
Since Inception rr_AverageAnnualReturnSinceInception (34.78%)
[1] The management fee is structured as a “unified fee,” out of which the Fund’s adviser pays all of the ordinary operating expenses of the Fund, except for the following expenses, each of which is paid by the Fund: the fee paid to the Adviser pursuant to the Investment Advisory Agreement, interest charges on any borrowings, taxes, brokerage commissions and other expenses incurred in placing orders for the purchase and sale of securities and other investment instruments, acquired fund fees and expenses, accrued deferred tax liability, extraordinary or other non-routine expenses, and distribution fees and expenses paid by the Fund under any distribution plan adopted pursuant to Rule 12b-1 under the Investment Company Act of 1940, as amended (the “1940 Act”).