Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB SMALL CAP GROWTH FUND
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is long-term growth of capital.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses paid 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 102.80% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	102.80%
Expense Example [Heading]	rr_ExpenseExampleHeading	Example:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund over 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 seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its assets in small capitalization companies. Small capitalization companies are defined as those companies with market capitalizations (share price multiplied by number of shares outstanding) within the capitalization range of the Russell 2000® Growth Index at the time of purchase.  As of August 31, 2012, the market capitalization of the largest company in the Russell 2000® Growth Index was approximately $4.621 billion, and the weighted average and median market capitalizations of the Russell 2000® Growth Index were approximately $1.431 billion and $584 million, respectively. The Fund maintains a diversified portfolio of investments consisting primarily of common stocks. The Fund may also invest in other equity securities such as preferred stocks, securities convertible or exchangeable into common stocks, rights, warrants, or real estate investment trusts. The Adviser expects to select investments for the Fund in companies that are broadly diversified over various industry groups. The Adviser manages the Fund's portfolio in an aggressive growth style. The Adviser believes that investments in small capitalization companies can have greater earnings and sales growth potential than larger capitalized companies and can offer substantial opportunities for long-term growth of capital. The Adviser's overall stock selections are based on its qualitative and quantitative assessment of a company's fundamental prospects and whether it has an above-average potential for long-term growth of capital. The Adviser expects to invest the Fund's net assets primarily in U.S. companies, but may gain exposure to foreign markets 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 will not invest more than 25% of the Fund's net assets directly in foreign companies. The Fund intends to hold some cash, short-term debt obligations, government securities or other high-quality investments for reserves to cover redemptions and unanticipated expenses, or to maintain liquidity while seeking appropriate investments.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Investing in a mutual fund has inherent risks, which could cause you to lose money. The principal risks of investing in the Fund, and the circumstances that could adversely affect the Fund's net asset value and total return, are listed below. ·  Market Risk: The value of the Fund's shares and the securities held by the        Fund can each decline in value. Even when the stock market in general is          rising, the stocks selected by the Adviser may decline. Prices of common          stocks of even the best managed, most profitable corporations are subject to      market risk, which means their stock prices can decline. In addition, swings      in investor psychology or significant trading by large institutional investors    can result in price fluctuations.                                                 ·  Smaller Capitalized Company Risk: Investments in small capitalization             companies may involve greater risks, as these companies tend to have limited      product lines, markets and financial or managerial resources. Small 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.                                  ·  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.                                                      ·  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    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.
Risk Lose Money [Text]	rr_RiskLoseMoney	Investing in a mutual fund has inherent risks, which could cause you to lose money.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
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 for the last calendar year, and the table compares the Fund's average annual returns with those of a broad measure of market performance. 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. Performance information is not presented for Institutional Class shares of the Fund because the Fund had not issued Institutional Class shares as of the date of this Prospectus.
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 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 as of December 31, 2011 (Investor Class)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	As of September 30, 2012, the Fund's year to date return was 14.52%. Best Quarter       Q4     2010      22.86% Worst Quarter      Q3     2011     -27.18%
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-deferred 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-deferred 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.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns as of December 31, 2011
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Russell 2000® Growth Index
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Russell 2000® Growth Index (reflects no deduction for fees, expenses or taxes)
1 Year	rr_AverageAnnualReturnYear01	(2.91%)
Since Inception	rr_AverageAnnualReturnSinceInception	14.51%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	(2.00%)
Advisory Fees	rr_ManagementFeesOverAssets	0.90%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	1.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.43%
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.18%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	2.25%	[2]
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-01-02
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	228
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	740
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,279
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,753
Annual Return 2011	rr_AnnualReturn2011	(13.93%)
Year to Date Return, Label	rr_YearToDateReturnLabel	year to date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	14.52%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2010
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	22.86%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2011
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(27.18%)
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	(13.93%)
Since Inception	rr_AverageAnnualReturnSinceInception	10.05%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class | After Taxes on Distributions
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	(15.34%)
Since Inception	rr_AverageAnnualReturnSinceInception	9.10%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Investor Class | After Taxes on Distributions and Sales
Risk Return [Abstract]	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	(9.05%)
Since Inception	rr_AverageAnnualReturnSinceInception	8.05%
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010
Jacob Small Cap Growth Fund (Prospectus Summary) | Jacob Small Cap Growth Fund | Institutional Class
Risk Return [Abstract]	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load)	rr_MaximumDeferredSalesChargeOverOfferingPrice	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed or exchanged within 30 days of purchase)	rr_RedemptionFeeOverRedemption	none
Advisory Fees	rr_ManagementFeesOverAssets	0.90%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	1.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.08%
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	(0.13%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.95%	[2]
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	2014-01-02
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	198
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	639
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,107
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,400
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01
Since Inception	rr_AverageAnnualReturnSinceInception
Inception Date	rr_AverageAnnualReturnInceptionDate	Feb. 01, 2010

[1] Jacob Asset Management of New York LLC, the Fund's investment adviser (the "Adviser"), has contractually agreed, through at least January 2, 2014, to waive up to 100% of its advisory fees to the extent that the Total Annual Fund Operating Expenses (excluding any taxes, interest, brokerage fees, and extraordinary expenses) exceed 2.25% or 1.95% for Investor Class shares and Institutional Class shares, respectively, of each class' average daily net assets. This fee waiver agreement does not extend to indirect expenses of any acquired funds. Pursuant to this fee waiver agreement, the Adviser is entitled to recoup any fees that it waived for a period of three years following such fee waivers to the extent that such recoupment will not cause the Fund to exceed any applicable expense limitation that was in place for the Fund when the fees were waived. Please note that the maximum waiver is 0.90%, which means that the Fund's overall expenses could exceed 2.25% for Investor Class shares or 1.95% for Institutional Class shares. This waiver agreement may only be terminated by the Board. Please also note that this fee waiver agreement is contingent upon the closing of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. Otherwise the fee waiver agreement currently in place for Investor Class shares of the Fund (which operates as described above with fees waived if expenses exceed 2.45%) will apply through at least January 2, 2014.

[2] Please note that the percentage of Annual Fund Operating Expenses shown is based on estimated amounts and on the amount of assets expected to transfer into the Fund as a result of the reorganization of the Jacob Small Cap Growth Fund II (formerly PineBridge US Small Cap Growth Fund) series of Jacob Funds II (formerly PineBridge Mutual Funds) into the Fund. If the Fund's average annual net assets during the current fiscal year are lower, the Fund's expense ratio would be higher than that shown above.