Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 01, 2012
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro Cap Growth Fund
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	JACOB MICRO 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.
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 micro capitalization companies. Micro capitalization companies are defined as those companies with market capitalizations (share price multiplied by number of shares outstanding) of (1) less than or equal to $600 million; or (2) within the capitalization range of the Russell Micro Cap® Growth Index at the time of purchase. As of August 31, 2012, the market capitalization of the largest company in the Russell Micro Cap® Growth Index was approximately $837 million, and the weighted average and median market capitalizations of the Russell Micro Cap® Growth Index were approximately $322 million and $149 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 micro 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.                                                 ·  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.                                ·  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	Performance information gives some indication of the risks of investing in the Fund by comparing the Fund's performance with a broad measure of market performance. Performance information is not presented because the Fund had not commenced investment operations as of the date of this Prospectus. In the future, the Fund will disclose performance information in a bar chart and performance table.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance information gives some indication of the risks of investing in the Fund by comparing the Fund's performance with a broad measure of market performance.
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro 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	1.20%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.35%
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.19%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	222
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	685
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	1,175
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,524
Jacob Micro Cap Growth Fund (Prospectus Summary) | Jacob Micro 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	1.20%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.64%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.84%	[1]
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	187
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	579
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	995
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	2,159

[1] 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 Micro Cap Growth Fund (formerly PineBridge US Micro 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.