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Label Element Value
Prospectus [Line Items] rr_ProspectusLineItems  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Nov. 30, 2019
Entity Registrant Name dei_EntityRegistrantName HENNESSY FUNDS TRUST
Entity Central Index Key dei_EntityCentralIndexKey 0000891944
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Feb. 28, 2020
Document Effective Date dei_DocumentEffectiveDate Feb. 28, 2020
Prospectus Date rr_ProspectusDate Feb. 28, 2020
Entity Inv Company Type dei_EntityInvCompanyType N-1A
Hennessy Cornerstone Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY CORNERSTONE GROWTH FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Cornerstone Growth Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 95% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 95.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund may invest in any company whose securities are listed on a U.S. national securities exchange and in any foreign company through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges.  The Fund invests in growth-oriented common stocks by utilizing a quantitative formula known as the Cornerstone Growth Strategy (the “Growth Strategy”). From the investable common stocks of public companies in the S&P Capital IQ Database with market capitalizations exceeding $175 million, the Growth Strategy identifies the 50 common stocks with the highest one-year price appreciation as of the date of purchase that also meet the following criteria:
•
Price-to-sales ratio below 1.5
The Growth Strategy uses price-to-sales as its value criterion because sales figures are more difficult for a company to manipulate than earnings and frequently provide a clearer picture of a company’s potential value.
•
Annual earnings that are higher than the previous year
The Growth Strategy considers improved earnings to be a key indicator of a company’s financial strength.
•
Positive stock price appreciation over the past three-month and six-month periods
The Growth Strategy considers stock price appreciation because it is often associated with positive fundamentals, such as strong growth or improving profitability.
The Fund purchases these 50 stocks weighted equally by dollar amount, with 2% of the portfolio’s assets invested in each. Using the Growth Strategy, the universe of stocks is re-screened and the portfolio is rebalanced annually, generally in the winter. Stocks meeting the Growth Strategy’s criteria not currently in the portfolio are purchased, and stocks that no longer meet the criteria are sold. Holdings of all stocks in the Fund that continue to meet the criteria are appropriately increased or decreased to result in an equal 2% weighting. Also, on a monthly basis, the Fund may elect to re-screen the universe of stocks and replace up to five of the lowest-performing in the portfolio with new stocks as determined by the Growth Strategy. If it does so, in addition to selling the lowest-performing stocks, the Fund will sell a portion of each of the remaining stocks in its portfolio on a pro rata basis so that it can purchase each of the new stocks to constitute 2% of its assets.
As of January 31, 2020, the average and median market capitalizations of the stocks held by the Fund were $2.9 billion and $9.0 billion, respectively.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to the Growth Strategy during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund in a given year are experiencing financial difficulty or are out of favor with investors.
Small-Sized and Medium-Sized Companies Risk: The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Foreign Securities Risk: The Fund may invest in foreign companies. There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies. Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes in the foreign country. Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
Growth and Value Investing Risk: Growth and value securities may perform differently from the market as a whole and may be out of favor with investors for periods of time. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Value securities may remain undervalued, their undervaluation may become more severe, or their perceived undervaluation may actually represent their intrinsic value.
High Portfolio Turnover Risk:  High portfolio turnover will produce higher transaction costs (such as brokerage commissions and dealer markups) that the Fund must pay, thus reducing the Fund’s performance. High portfolio turnover may also result in higher taxes when Fund shares are held in a taxable account.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell 2000® Index and the S&P 500® Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the Hennessy Cornerstone Growth Fund, a series of Hennessy Mutual Funds, Inc. (the “Predecessor Growth Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Growth Fund, which had the same investment adviser and the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell 2000® Index and the S&P 500® Index.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY CORNERSTONE GROWTH FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 23.23% for the quarter ended March 31, 2012, and the lowest quarterly return was -29.48% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 23.23%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (29.48%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Hennessy Cornerstone Growth Fund | Russell 2000® Index (reflects no deductions for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 2000® Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 25.52%
5 Years rr_AverageAnnualReturnYear05 8.23%
10 Years rr_AverageAnnualReturnYear10 11.83%
Hennessy Cornerstone Growth Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Cornerstone Growth Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFCGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.35%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.45%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.34%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 136
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 425
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 734
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,613
Annual Return 2010 rr_AnnualReturn2010 11.50%
Annual Return 2011 rr_AnnualReturn2011 (10.78%)
Annual Return 2012 rr_AnnualReturn2012 30.31%
Annual Return 2013 rr_AnnualReturn2013 35.89%
Annual Return 2014 rr_AnnualReturn2014 13.82%
Annual Return 2015 rr_AnnualReturn2015 (1.09%)
Annual Return 2016 rr_AnnualReturn2016 8.37%
Annual Return 2017 rr_AnnualReturn2017 16.60%
Annual Return 2018 rr_AnnualReturn2018 (21.22%)
Annual Return 2019 rr_AnnualReturn2019 20.70%
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Growth Fund – Investor Return before taxes
1 Year rr_AverageAnnualReturnYear01 20.70%
5 Years rr_AverageAnnualReturnYear05 3.51%
10 Years rr_AverageAnnualReturnYear10 9.07%
Hennessy Cornerstone Growth Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Growth Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 20.70%
5 Years rr_AverageAnnualReturnYear05 3.07%
10 Years rr_AverageAnnualReturnYear10 8.84%
Hennessy Cornerstone Growth Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Growth Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 12.26%
5 Years rr_AverageAnnualReturnYear05 2.68%
10 Years rr_AverageAnnualReturnYear10 7.44%
Hennessy Cornerstone Growth Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HICGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.27%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.27%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.01%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 103
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 322
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 558
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,236
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Growth Fund – Institutional Return before taxes
1 Year rr_AverageAnnualReturnYear01 21.05%
5 Years rr_AverageAnnualReturnYear05 3.83%
10 Years rr_AverageAnnualReturnYear10 9.42%
Hennessy Focus Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY FOCUS FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Focus Fund seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 2% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 2.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests primarily in domestic companies listed on U.S. national securities exchanges. The Fund may also invest in (i) foreign companies listed on U.S. national securities exchanges, (ii) foreign companies through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges and, (iii) foreign companies traded on foreign exchanges.  Investments will consist primarily of common stocks, but may include preferred stocks, warrants, options, equity-like instruments, and debt instruments.  The Fund invests without regard to market capitalization.
The Portfolio Managers implement the Fund’s strategy by focusing on approximately 20 companies whose valuations in the market are modest, that earn higher than average economic returns, that are well managed, and that have ample opportunity to reinvest excess profits at above-average rates. The Fund's holdings are coviction-weighted. Once a potential investment is identified, the Portfolio Managers attempt to purchase shares at a price they believe represents a discount to a conservative estimate of the company’s intrinsic value. Generally, the Portfolio Managers may sell a business for a variety of reasons, including (i) source of funds for what they believe is a superior investment idea, (ii) adverse change in their assessment of a business’s quality, growth, or management, (iii) valuation, or (iv) risk management at the company or portfolio level.
The Fund may from time to time hold a significant portion of its portfolio in cash or cash equivalent instruments.  If market conditions reduce the availability of securities with acceptable valuations, the Fund may, for extended periods, hold larger than usual cash reserves until securities with acceptable valuations become available.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The Fund is currently substantially invested in the consumer discretionary, financials, and industrials sectors, and its performance is therefore tied closely to, and affected by, developments in these industries. Companies in the consumer discretionary sector may be affected by commodity price volatility, consumer preferences, competition, changing demographics, and labor relations. These companies depend heavily on disposable household income and consumer spending, and social trends and marketing campaigns may significantly affect demand for their products. Consumer discretionary companies may also lose value more quickly in periods of economic downturns because their products are viewed as nonessential luxury items. Financial services companies may be adversely affected by changes in the regulatory environment, interest rate fluctuations, and other factors. Finally, companies in the industrials sector may be adversely affected by changes in the supply of and demand for products and services, product obsolescence, environmental liabilities, and product liability.
Non-Diversification Risk: The Fund is non-diversified under the Investment Company Act and employs a concentrated investment strategy. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified, less concentrated fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Temporary Defensive Positions Risk: From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political conditions.  To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective.  For temporary defensive purposes, the Fund may invest in cash or short-term obligations.
Small-Sized and Medium-Sized Companies Risk: The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Foreign Securities Risk: The Fund may invest in foreign companies. There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies. Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes in the foreign country. Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
Real Estate Investment Risk: The Fund invests in real estate investments, including real estate investment trusts (REITs), and is therefore subject to risks associated with the real estate market.  Real estate investments are particularly susceptible to economic downturns, changes in regulations, and fluctuating interest rates.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act and employs a concentrated investment strategy. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified, less concentrated fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 3000® Index, as well as an additional index that includes securities with market capitalizations and certain other attributes similar to the average market capitalization and attributes of the securities in which the Fund invests, the Russell MidCap® Growth Index.  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the FBR Focus Fund (the “Predecessor Focus Fund”). The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Focus Fund, which had the same investment objective and substantially similar investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 3000® Index, as well as an additional index that includes securities with market capitalizations and certain other attributes similar to the average market capitalization and attributes of the securities in which the Fund invests, the Russell MidCap® Growth Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell MidCap® Growth Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments with market capitalizations and certain other attributes similar to the average market capitalization and attributes of the securities held by the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY FOCUS FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 18.96% for the quarter ended December 31, 2011, and the lowest quarterly return was -14.33% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.96%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (14.33%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell MidCap® Growth Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments with market capitalizations and certain other attributes similar to the average market capitalization and attributes of the securities held by the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.  After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Hennessy Focus Fund | Russell 3000® Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 3000® Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 31.02%
5 Years rr_AverageAnnualReturnYear05 11.24%
10 Years rr_AverageAnnualReturnYear10 13.42%
Hennessy Focus Fund | Russell Midcap® Growth Index (reflects no deduction for fees, expenses and taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell MidCap® Growth Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 35.47%
5 Years rr_AverageAnnualReturnYear05 11.60%
10 Years rr_AverageAnnualReturnYear10 14.24%
Hennessy Focus Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFCSX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.32%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.42%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.47%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 150
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 465
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 803
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,757
Annual Return 2010 rr_AnnualReturn2010 24.55%
Annual Return 2011 rr_AnnualReturn2011 3.63%
Annual Return 2012 rr_AnnualReturn2012 16.64%
Annual Return 2013 rr_AnnualReturn2013 35.33%
Annual Return 2014 rr_AnnualReturn2014 10.20%
Annual Return 2015 rr_AnnualReturn2015 2.88%
Annual Return 2016 rr_AnnualReturn2016 7.16%
Annual Return 2017 rr_AnnualReturn2017 19.27%
Annual Return 2018 rr_AnnualReturn2018 (10.47%)
Annual Return 2019 rr_AnnualReturn2019 34.86%
Label rr_AverageAnnualReturnLabel Hennessy Focus Fund – Investor Return before taxes
1 Year rr_AverageAnnualReturnYear01 34.86%
5 Years rr_AverageAnnualReturnYear05 9.69%
10 Years rr_AverageAnnualReturnYear10 13.55%
Hennessy Focus Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Focus Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 31.77%
5 Years rr_AverageAnnualReturnYear05 8.24%
10 Years rr_AverageAnnualReturnYear10 12.18%
Hennessy Focus Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Focus Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 22.89%
5 Years rr_AverageAnnualReturnYear05 7.51%
10 Years rr_AverageAnnualReturnYear10 11.15%
Hennessy Focus Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFCIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.22%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.22%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 114
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 356
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 617
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,363
Label rr_AverageAnnualReturnLabel Hennessy Focus Fund – Institutional Return before taxes
1 Year rr_AverageAnnualReturnYear01 35.34%
5 Years rr_AverageAnnualReturnYear05 10.09%
10 Years rr_AverageAnnualReturnYear10 13.92%
Hennessy Cornerstone Mid Cap 30 Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY CORNERSTONE MID CAP 30 FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Cornerstone Mid Cap 30 Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 70% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 70.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund may invest in any company listed on a U.S. national securities exchange, but specifically excludes American Depositary Receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in mid-cap growth-oriented common stocks by utilizing a quantitative formula known as the Cornerstone Mid Cap 30 Formula (the “Mid Cap 30 Formula”). From the investable common stocks of public companies in the S&P Capital IQ Database with market capitalizations between $1 billion and $10 billion, the Mid Cap 30 Formula identifies the 30 common stocks with the highest one-year price appreciation as of the date of purchase that also meet the following criteria:

•
Price-to-sales ratio below 1.5 
The Mid Cap 30 Formula uses price-to-sales as its value criterion because sales figures are more difficult for a company to manipulate than earnings and frequently provide a clearer picture of a company’s potential value.
•
Annual earnings that are higher than the previous year
The Mid Cap 30 Formula considers improved earnings to be a key indicator of a company’s financial strength.
•
Positive stock price appreciation over the past three-month and six-month periods
The Mid Cap 30 Formula considers stock price appreciation because it is often associated with positive fundamentals, such as strong growth or improving profitability.
The Fund purchases these 30 stocks weighted equally by dollar amount, with 3.33% of the portfolio’s assets invested in each. Using the Mid Cap 30 Formula, the universe of stocks is re-screened and the portfolio is rebalanced annually, generally in the fall. Stocks meeting the Mid Cap 30 Formula’s criteria not currently in the portfolio are purchased, and stocks that no longer meet the criteria are sold. Holdings of all stocks in the Fund that continue to meet the criteria are appropriately increased or decreased to result in an equal 3.33% weighting.  Also, on a monthly basis, the Fund may elect to re-screen the universe of stocks and replace up to three of the lowest-performing stocks in the portfolio with new stocks as determined by the Mid Cap 30 Formula.  If it does so, in addition to selling the lowest-performing stocks, the Fund will sell a portion of each of the remaining stocks in its portfolio on a pro rata basis so that it can purchase each of the new stocks to constitute 3.33% of its assets.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to the Mid Cap 30 Formula during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund in a given year are experiencing financial difficulty or are out of favor with investors.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The industries in which the Fund concentrates its investments at any given time are solely the result of the Mid Cap 30 Formula and may change significantly when the Fund is rebalanced. The Fund is currently substantially invested in the consumer discretionary sector, and its performance is therefore tied closely to, and affected by, industry developments. Companies in the consumer discretionary sector may be affected by commodity price volatility, consumer preferences, competition, changing demographics, and labor relations. These companies depend heavily on disposable household income and consumer spending, and social trends and marketing campaigns may significantly affect demand for their products. Consumer discretionary companies may also lose value more quickly in periods of economic downturns because their products are viewed as nonessential luxury items.
Small-Sized and Medium-Sized Companies Risk: The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies.  Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Growth and Value Investing Risk: Growth and value securities may perform differently from the market as a whole and may be out of favor with investors for periods of time. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Value securities may remain undervalued, their undervaluation may become more severe, or their perceived undervaluation may actually represent their intrinsic value.
High Portfolio Turnover Risk:  High portfolio turnover will produce higher transaction costs (such as brokerage commissions and dealer markups) that the Fund must pay, thus reducing the Fund’s performance. High portfolio turnover may also result in higher taxes when Fund shares are held in a taxable account.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the types of securities in which the Fund invests, the Russell Midcap® Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the Hennessy Cornerstone Mid Cap 30 Fund, a series of Hennessy Mutual Funds, Inc. (the “Predecessor Mid Cap 30 Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Mid Cap 30 Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the types of securities in which the Fund invests, the Russell Midcap® Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell Midcap® Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY CORNERSTONE MID CAP 30 FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 15.10% for the quarter ended March 31, 2013, and the lowest quarterly return was -21.54% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.10%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.54%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell Midcap® Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy Cornerstone Mid Cap 30 Fund | Russell Midcap® Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell Midcap® Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 30.54%
5 Years rr_AverageAnnualReturnYear05 9.33%
10 Years rr_AverageAnnualReturnYear10 13.19%
Hennessy Cornerstone Mid Cap 30 Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Cornerstone Mid Cap 30 Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFMDX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.37%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.47%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.36%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 138
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 431
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 745
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,635
Annual Return 2010 rr_AnnualReturn2010 27.26%
Annual Return 2011 rr_AnnualReturn2011 4.05%
Annual Return 2012 rr_AnnualReturn2012 14.10%
Annual Return 2013 rr_AnnualReturn2013 29.63%
Annual Return 2014 rr_AnnualReturn2014 16.44%
Annual Return 2015 rr_AnnualReturn2015 0.02%
Annual Return 2016 rr_AnnualReturn2016 5.82%
Annual Return 2017 rr_AnnualReturn2017 20.51%
Annual Return 2018 rr_AnnualReturn2018 (22.78%)
Annual Return 2019 rr_AnnualReturn2019 15.76%
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Mid Cap 30 Fund – Investor Return before taxes
1 Year rr_AverageAnnualReturnYear01 15.76%
5 Years rr_AverageAnnualReturnYear05 2.66%
10 Years rr_AverageAnnualReturnYear10 10.03%
Hennessy Cornerstone Mid Cap 30 Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Mid Cap 30 Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 15.76%
5 Years rr_AverageAnnualReturnYear05 0.40%
10 Years rr_AverageAnnualReturnYear10 8.45%
Hennessy Cornerstone Mid Cap 30 Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Mid Cap 30 Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 9.33%
5 Years rr_AverageAnnualReturnYear05 2.01%
10 Years rr_AverageAnnualReturnYear10 8.22%
Hennessy Cornerstone Mid Cap 30 Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HIMDX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.26%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 318
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 552
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,225
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Mid Cap 30 Fund – Institutional Return before taxes
1 Year rr_AverageAnnualReturnYear01 16.02%
5 Years rr_AverageAnnualReturnYear05 2.99%
10 Years rr_AverageAnnualReturnYear10 10.40%
Hennessy Cornerstone Large Growth Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY CORNERSTONE LARGE GROWTH FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Cornerstone Large Growth Fund seeks long-term growth of capital.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 57% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 57.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund may invest in any company listed on a U.S. national securities exchange, but specifically excludes American Depositary Receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges. The Fund invests in growth-oriented common stocks of larger companies by utilizing a quantitative formula known as the Cornerstone Large Growth Formula (the “Large Growth Formula”). Beginning with the investable common stocks of public companies in the S&P Capital IQ Database, the Large Growth Formula identifies the 50 common stocks that meet the following criteria, in the specified order:
1)
Above-average market capitalization
2)
Price-to-cash flow ratio less than the median of the remaining securites
3)
Positive total capital
4)
Highest one-year return on total capital
The Fund purchases these 50 stocks weighted equally by dollar amount, with 2% of the portfolio’s assets invested in each.  Using the Large Growth Formula, the universe of stocks is re-screened and the portfolio is rebalanced annually, generally in the winter.  Stocks meeting the Large Growth Formula’s criteria not currently in the portfolio are purchased, and stocks that no longer meet the criteria are sold.  Holdings of all stocks in the Fund that continue to meet the criteria are appropriately increased or decreased to result in an equal 2% weighting.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with an investment in the Fund. The value of an investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to the Large Growth Formula during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund in a given year are experiencing financial difficulty or are out of favor with investors.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The industries in which the Fund concentrates its investments at any given time are solely the result of the Large Growth Formula and may change significantly when the Fund is rebalanced. The Fund is currently substantially invested in the consumer discretionary and industrials sectors, and its performance is therefore tied closely to, and affected by, developments in these industries. Companies in the consumer discretionary sector may be affected by commodity price volatility, consumer preferences, competition, changing demographics, and labor relations. These companies depend heavily on disposable household income and consumer spending, and social trends and marketing campaigns may significantly affect demand for their products. Consumer discretionary companies may also lose value more quickly in periods of economic downturns because their products are viewed as nonessential luxury items. Companies in the industrials sector may be adversely affected by changes in the supply of and demand for products and services, product obsolescence, environmental liabilities, and product liability.
Medium-Sized Company Risk: The Fund may invest in medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. 
Growth and Value Investing Risk: Growth and value securities may perform differently from the market as a whole and may be out of favor with investors for periods of time. Growth securities typically are very sensitive to market movements because their market prices tend to reflect future expectations. When it appears those expectations will not be met, the prices of growth securities typically fall. Value securities may remain undervalued, their undervaluation may become more severe, or their perceived undervaluation may actually represent their intrinsic value.
Risk Lose Money [Text] rr_RiskLoseMoney The value of an investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell 1000® Index and the S&P 500® Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell 1000® Index and the S&P 500® Index.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY CORNERSTONE LARGE GROWTH FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 11.76% for the quarter ended September 30, 2010, and the lowest quarterly return was -15.98% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.76%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (15.98%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy Cornerstone Large Growth Fund | Russell 1000® Index (reflects no deduction for fees, expense or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 1000® Index reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 31.43%
5 Years rr_AverageAnnualReturnYear05 11.48%
10 Years rr_AverageAnnualReturnYear10 13.54%
Hennessy Cornerstone Large Growth Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Cornerstone Large Growth Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFLGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.32%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.42%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.31%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 133
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 415
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 718
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,579
Annual Return 2010 rr_AnnualReturn2010 18.85%
Annual Return 2011 rr_AnnualReturn2011 2.59%
Annual Return 2012 rr_AnnualReturn2012 10.44%
Annual Return 2013 rr_AnnualReturn2013 33.79%
Annual Return 2014 rr_AnnualReturn2014 16.18%
Annual Return 2015 rr_AnnualReturn2015 (6.60%)
Annual Return 2016 rr_AnnualReturn2016 14.69%
Annual Return 2017 rr_AnnualReturn2017 17.08%
Annual Return 2018 rr_AnnualReturn2018 (8.98%)
Annual Return 2019 rr_AnnualReturn2019 27.53%
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Large Growth Fund – Investor Return before taxes
1 Year rr_AverageAnnualReturnYear01 27.53%
5 Years rr_AverageAnnualReturnYear05 7.80%
10 Years rr_AverageAnnualReturnYear10 11.79%
Hennessy Cornerstone Large Growth Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Large Growth Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 26.79%
5 Years rr_AverageAnnualReturnYear05 5.15%
10 Years rr_AverageAnnualReturnYear10 9.46%
Hennessy Cornerstone Large Growth Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Large Growth Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 16.81%
5 Years rr_AverageAnnualReturnYear05 5.63%
10 Years rr_AverageAnnualReturnYear10 9.31%
Hennessy Cornerstone Large Growth Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HILGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.26%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.26%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 318
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 552
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,225
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Large Growth Fund – Institutional Return before taxes
1 Year rr_AverageAnnualReturnYear01 27.82%
5 Years rr_AverageAnnualReturnYear05 8.07%
10 Years rr_AverageAnnualReturnYear10 12.07%
Hennessy Cornerstone Value Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY CORNERSTONE VALUE FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Cornerstone Value Fund seeks total return, consisting of capital appreciation and current income.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 27% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 27.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund may invest in any company whose securities are listed on a U.S. national securities exchange and in any foreign company through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges. The Fund invests in larger, dividend-paying common stocks by utilizing a quantitative formula known as the Cornerstone Value Strategy (the “Value Strategy”). From the investable common stocks of public companies in the S&P Capital IQ Database, the Value Strategy identifies the 50 common stocks with the highest dividend yield as of the date of purchase that also meet the following criteria:
•
Above-average market capitalization
•
Above-average number of shares outstanding
•
Twelve-month sales that are 50% greater than the average
•
Above-average cash flow
The Fund purchases these 50 stocks weighted equally by dollar amount, with 2% of the portfolio’s assets invested in each. Using the Value Strategy, the universe of stocks is re-screened and the portfolio is rebalanced annually, generally in the winter. Stocks meeting the Value Strategy’s criteria not currently in the portfolio are purchased, and stocks that no longer meet the criteria are sold. Holdings of all stocks in the Fund that continue to meet the criteria are appropriately increased or decreased to result in an equal 2% weighting.
As of January 31, 2020, the average and median market capitalizations of the stocks held by the Fund were $113.2 billion and $94.3 billion, respectively.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to the Value Strategy during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund’s portfolio in a given year are experiencing financial difficulty or are out of favor with investors.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The industries in which the Fund concentrates its investments at any given time are solely the result of the Value Strategy and may change significantly when the Fund is rebalanced. The Fund is currently substantially invested in the consumer staples and energy industries, and its performance is therefore tied closely to, and affected by, developments in these industries. Companies in the consumer staples sector may be affected by commodity production and pricing, consumer confidence, spending, and preferences, product cycles, marketing, competition, and government regulation. In particular, the success of consumer staples is often strongly affected by fads and marketing campaigns, as well as government regulations. Energy companies may be adversely affected by fluctuations in commodity prices, reduced supply or demand of energy commodities, the disruption of energy supplies transported on interstate pipelines, depletion of reserves, extreme weather or environmental hazards, accidents or other operating issues, changes in the regulatory environment, slowdowns in new construction, rising interest rates, and terrorist threats on energy assets.
Medium-Sized Companies Risk: The Fund may invest in medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies.
Value Investing Risk: Value securities may perform differently from the market as a whole and may be out of favor with investors for periods of time. Value securities may remain undervalued, their undervaluation may become more severe, or their perceived undervaluation may actually represent their intrinsic value.
Foreign Securities Risk: The Fund may invest in foreign companies. There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies. Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes in the foreign country. Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the types of securities in which the Fund invests, the Russell 1000® Value Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the Hennessy Cornerstone Value Fund, a series of Hennessy Mutual Funds, Inc. (the “Predecessor Value Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Value Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the types of securities in which the Fund invests, the Russell 1000® Value Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell 1000® Value Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY CORNERSTONE VALUE FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 11.96% for the quarter ended September 30, 2010, and the lowest quarterly return was -12.67% for the quarter ended December 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.96%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (12.67%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. 
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell 1000® Value Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy Cornerstone Value Fund | Russell 1000® Value Index (reflects no deductions for fees, expenses and taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 1000® Value Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 26.54%
5 Years rr_AverageAnnualReturnYear05 8.29%
10 Years rr_AverageAnnualReturnYear10 11.80%
Hennessy Cornerstone Value Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Cornerstone Value Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HFCVX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.24%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.34%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.23%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 125
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 390
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 676
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,489
Annual Return 2010 rr_AnnualReturn2010 12.51%
Annual Return 2011 rr_AnnualReturn2011 6.47%
Annual Return 2012 rr_AnnualReturn2012 11.94%
Annual Return 2013 rr_AnnualReturn2013 26.40%
Annual Return 2014 rr_AnnualReturn2014 8.86%
Annual Return 2015 rr_AnnualReturn2015 (6.37%)
Annual Return 2016 rr_AnnualReturn2016 17.25%
Annual Return 2017 rr_AnnualReturn2017 19.16%
Annual Return 2018 rr_AnnualReturn2018 (9.34%)
Annual Return 2019 rr_AnnualReturn2019 20.79%
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Value Fund – Investor Return before taxes
1 Year rr_AverageAnnualReturnYear01 20.79%
5 Years rr_AverageAnnualReturnYear05 7.46%
10 Years rr_AverageAnnualReturnYear10 10.21%
Hennessy Cornerstone Value Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Value Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 18.97%
5 Years rr_AverageAnnualReturnYear05 5.30%
10 Years rr_AverageAnnualReturnYear10 8.83%
Hennessy Cornerstone Value Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Value Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 13.58%
5 Years rr_AverageAnnualReturnYear05 5.51%
10 Years rr_AverageAnnualReturnYear10 8.21%
Hennessy Cornerstone Value Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HICVX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.34%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.34%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.08%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 110
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 343
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 595
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,317
Label rr_AverageAnnualReturnLabel Hennessy Cornerstone Value Fund – Institutional Return before taxes
1 Year rr_AverageAnnualReturnYear01 20.98%
5 Years rr_AverageAnnualReturnYear05 7.66%
10 Years rr_AverageAnnualReturnYear10 10.47%
Hennessy Total Return Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY TOTAL RETURN FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Total Return Fund seeks total return, consisting of capital appreciation and current income.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 30% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 30.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 the assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests in the 10 highest dividend-yielding Dow Jones Industrial Average (“DJIA”) stocks (known as the “Dogs of the Dow”) and in U.S. Treasury securities with a maturity of less than one year.
The Fund invests approximately 50% of its assets in the 10 Dogs of the Dow stocks in roughly equal dollar amounts and approximately 50% of its assets in U.S. Treasury securities with a maturity of less than one year. The Fund then utilizes a borrowing strategy that allows the Fund’s performance to approximate what it would be if the Fund had an asset allocation of roughly 75% Dogs of the Dow stocks and 25% U.S. Treasury securities. The Fund typically borrows money by entering into reverse repurchase agreements secured by its portfolio of U.S. Treasury securities.
The total portfolio is divided into multiple sub-portfolios, each of which uses the Dogs of the Dow strategy. On various dates throughout the year, each of these sub-portfolios is reviewed. In a review, the Investment Manager determines the 10 highest yielding common stocks in the DJIA by annualizing the last quarterly or semi-annual ordinary dividend declared on each stock and dividing the result by the market value of that stock. The Fund then purchases those stocks in approximately equal amounts for the sub-portfolio being reviewed. From time to time, the Fund also may purchase an approximately equal amount of U.S. Treasury securities having a remaining maturity of less than one year for the sub-portfolio being reviewed. On the next date, another sub-portfolio is reviewed in a similar manner.
Regardless of whether they remain in the DJIA or retain the characteristics of Dogs of the Dow Stocks, the Fund generally holds the stock investments within each sub-portfolio for one year, at which time the applicable sub-portfolio is up for another review. At the end of the one-year period, the Fund sells any stocks in the applicable sub-portfolio that are no longer Dogs of the Dow stocks and replaces them with stocks that are Dogs of the Dow stocks. Additionally, the Fund may sell a portion of the stocks that remain in the applicable sub-portfolio so that the rebalanced portion of the sub-portfolio adheres to the Fund’s asset allocation strategy.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
Although a portion of the Fund’s portfolio is invested in U.S. Treasury securities, there are market and investment risks associated with an investment in the Fund, as there are with any security. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to its strategy during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund’s portfolio in a given year are experiencing financial difficulty or are out of favor with investors.
Non-Diversification Risk: The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Borrowing Risk: The Fund borrows against its investments by entering into reverse repurchase agreements secured by its portfolio of U.S. Treasury securities. Purchasing U.S. Treasury securities with borrowed money is an investment technique that increases investment risk because if the securities purchased with borrowed money decline in value, the Fund’s losses would be greater than if it had used cash to make purchases. Also, the Fund incurs interest costs when it borrows money, and these costs may exceed the investment returns it earns on the securities purchased with borrowed money. Reverse repurchase agreements involve the risk that the buyer of the securities sold by the Fund might be unable to deliver them when the Fund seeks to repurchase.  If the buyer of securities under a reverse repurchase agreement files for bankruptcy or becomes insolvent, the buyer, trustee, or receiver may receive an extension of time to determine whether to enforce the Fund’s obligation to repurchase the securities, and the Fund’s use of the proceeds from the reverse repurchase agreement may effectively be restricted pending such decision.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Hennessy Total Return Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the DJIA, as well as an additional index that reflects the types of securities in which the Fund invests, the 75/25 Blended DJIA/Treasury Index (which consists of 75% common stocks represented by the DJIA and 25% short-duration Treasury securities represented by the ICE BofAML U.S. 3-Month Treasury Bill Index). For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the Hennessy Total Return Fund, a series of The Hennessy Funds, Inc. (the “Predecessor Total Return Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Total Return Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Hennessy Total Return Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the DJIA, as well as an additional index that reflects the types of securities in which the Fund invests, the 75/25 Blended DJIA/Treasury Index (which consists of 75% common stocks represented by the DJIA and 25% short-duration Treasury securities represented by the ICE BofAML U.S. 3-Month Treasury Bill Index).
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the 75/25 Blended DJIA/Treasury Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY TOTAL RETURN FUND CALENDAR YEAR TOTAL RETURNS
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown on the bar chart, the Fund’s highest quarterly return was 11.75% for the quarter ended September 30, 2010, and the lowest quarterly return was -5.95% for the quarter ended June 30, 2010.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 11.75%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (5.95%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the 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 Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the 75/25 Blended DJIA/Treasury Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the 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.
Hennessy Total Return Fund | 75/25 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel 75/25 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 19.34%
5 Years rr_AverageAnnualReturnYear05 9.75%
10 Years rr_AverageAnnualReturnYear10 10.21%
Hennessy Total Return Fund | Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 25.34%
5 Years rr_AverageAnnualReturnYear05 12.59%
10 Years rr_AverageAnnualReturnYear10 13.40%
Hennessy Total Return Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HDOGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 1.09%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.38% [1]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.57%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 2.32%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 235
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 724
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,240
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,656
Annual Return 2010 rr_AnnualReturn2010 14.09%
Annual Return 2011 rr_AnnualReturn2011 10.81%
Annual Return 2012 rr_AnnualReturn2012 6.77%
Annual Return 2013 rr_AnnualReturn2013 18.52%
Annual Return 2014 rr_AnnualReturn2014 5.85%
Annual Return 2015 rr_AnnualReturn2015 1.00%
Annual Return 2016 rr_AnnualReturn2016 12.92%
Annual Return 2017 rr_AnnualReturn2017 11.17%
Annual Return 2018 rr_AnnualReturn2018 0.11%
Annual Return 2019 rr_AnnualReturn2019 12.56%
Label rr_AverageAnnualReturnLabel Hennessy Total Return Fund Return before taxes
1 Year rr_AverageAnnualReturnYear01 12.56%
5 Years rr_AverageAnnualReturnYear05 7.39%
10 Years rr_AverageAnnualReturnYear10 9.24%
Hennessy Total Return Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Total Return Fund Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 12.09%
5 Years rr_AverageAnnualReturnYear05 5.65%
10 Years rr_AverageAnnualReturnYear10 8.03%
Hennessy Total Return Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Total Return Fund Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 7.75%
5 Years rr_AverageAnnualReturnYear05 5.55%
10 Years rr_AverageAnnualReturnYear10 7.39%
Hennessy Equity and Income Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY EQUITY AND INCOME FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Equity and Income Fund seeks long-term capital growth and current income.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 16% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 16.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund is designed as a balanced fund that seeks income and long-term capital appreciation with reduced volatility of returns.  The Portfolio Managers’ approach places a focus on seeking downside protection.  Under normal circumstances, the Fund will invest approximately 60% of its assets in equity securities and approximately 40% of its assets in fixed income securities, but this allocation mix may change over time based on the Investment Manager’s view of economic and investment conditions and underlying security values.
The Fund invests primarily in the securities of companies listed on U.S. national securities exchanges, including common stock, preferred stock, convertible securities, and high-quality corporate, agency, and government bonds.  The Fund may also invest in mortgage-backed and asset-backed securities and in foreign securities, including American Depositary Receipts or other types of depositary receipts, which are U.S. dollar-denominated securities of foreign issuers listed on U.S. national securities exchanges.  The Fund may invest directly in fixed income securities or it may invest indirectly in fixed income securities by investing in other investment companies (including exchange-traded funds, referred to as ETFs) that invest in fixed income securities.  The Fund invests without regard to market capitalization.
EQUITY ALLOCATION
The equity Portfolio Managers utilize a fundamental, value-oriented investment approach, focusing on larger, high-quality companies with demonstrated market dominance, low business risk, and solid long-term growth prospects.  In choosing which securities to purchase, the equity Portfolio Managers give consideration to companies that have shareholder-oriented management, with a history of alignment with shareholder interests through stock incentives, insider buying, and corporate stock buybacks.  Many of the stocks held by the Fund are expected to pay dividends.  Generally, the equity Portfolio Managers may choose to sell a position if it begins to have a significant negative effect on total portfolio value, if they believe it has reached an excessive valuation level, when the company’s fundamentals deteriorate, or when a more attractive candidate is identified through the screening process.
FIXED INCOME ALLOCATION
The fixed income Portfolio Managers focus on higher quality, intermediate-term fixed income securities, but they may invest up to 10% of the Fund’s assets in high-yield bonds (commonly known as “junk bonds”).
The fixed income Portfolio Managers continuously analyze and assess the variables that influence bond prices. They use this proprietary approach, which combines economic data and technical factors, to evaluate the probability of interest rate movements in order to manage the duration of the portfolio in an effort to mitigate downside risk and maximize total return.  They purchase and sell securities in accordance with these principles to meet previously identified sector allocations, duration targets, and curve strategies for the fixed income allocation of the Fund.
As of January 31, 2020, the bonds and cash equivalents held in the fixed income allocation of the Fund had a dollar-weighted average effective maturity of 7.7 years.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Debt Investments Risk: The yields and principal values of debt securities fluctuate. Generally, values of debt securities change inversely with interest rates.  That is, as interest rates go up, the values of debt securities tend to go down and vice versa.  These fluctuations tend to increase in magnitude as a bond’s maturity increases such that a longer-term bond will increase or decrease more significantly with a given change in interest rates than a shorter-term bond.  Many debt securities utilize LIBOR as the reference or benchmark rate for variable interest rate calculations. However, LIBOR has come under pressure following manipulation allegations. Further, the United Kingdom’s Financial Conduct Authority, which regulates LIBOR, has announced that it intends to stop encouraging or compelling banks to submit rates for the calculation of LIBOR rates after 2021, and it appears likely that LIBOR will be discontinued or modified by 2021. If LIBOR in its current form does not survive or if an alternative index is chosen, the market value or liquidity of securities with distributions or interest rates based on LIBOR could be adversely affected.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The Fund is currently substantially invested in the financial services sector, and its performance is therefore affected by industry developments. Financial services companies may be adversely affected by changes in the regulatory environment, interest rate changes, and other factors.
Foreign Securities Risk: The Fund may invest in foreign companies.  There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies.  Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes the foreign country.  Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
High-Yield Investments Risk: The Fund may invest a portion of its assets in lower-rated, high-yielding bonds (commonly known as “junk bonds”).  These bonds have a greater degree of default risk than higher-rated bonds.  Default risk is the possibility that the issuer of a debt security will fail to make timely payments of principal or interest to the Fund.
Mortgage-Backed and Asset-Backed Securities Risk: Mortgage-backed and asset-backed securities are subject to the risk that borrowers default on their loans and the risk that borrowers prepay some or all of the principal owed to the issuer, in each case causing the investments to fail to realize expected returns.
Investment Company Securities Risk: When the Fund invests in another investment company (including an ETF), it will indirectly bear its proportionate share of any fees and expenses payable directly by the other investment company. Therefore, the Fund will incur higher expenses, many of which may be duplicative. In addition, the Fund may be affected by the other investment company’s losses and the level of risk arising from its investment practices (such as the use of leverage). The Fund has no control over the risks taken by the other investment company.
ETF Risk:  In addition to risks generally associated with investments in investment company securities, investments in ETFs are subject to the following additional risks that do not apply to non-ETFs: (i) an ETF’s shares may trade at a market price that is above or below their net asset value; (ii) an active trading market for an ETF’s shares may not develop or be maintained; (iii) the ETF may employ an investment strategy that utilizes high leverage ratios; and (iv) trading of an ETF’s shares may be halted if the listing exchange’s officials deem such action appropriate, the shares are de-listed from the exchange, or the activation of market-wide “circuit breakers” (which are tied to large decreases in stock prices) halts stock trading generally.
Temporary Defensive Positions Risk: From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political conditions.  To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective.  For temporary defensive purposes, the Fund may invest in cash or short-term obligations.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects types of securities in which the Fund invests, the Blended Balanced Index (which consists of 60% common stocks represented by the S&P 500® Index and 40% bonds represented by the Bloomberg Barclays Intermediate U.S. Government/Credit Index).  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the FBR Balanced Fund (the “Predecessor Equity and Income Fund”).  The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Equity and Income Fund, which had the same investment objective and substantially similar investment strategy as the Fund.  The Predecessor Equity and Income Fund was the investment successor to the AFBA 5Star Balanced Fund (the “AFBA Predecessor Balanced Fund”).  The performance information provided for periods on or prior to March 12, 2010, is historical information for the Advisor Class shares of the AFBA Predecessor Balanced Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects types of securities in which the Fund invests, the Blended Balanced Index (which consists of 60% common stocks represented by the S&P 500® Index and 40% bonds represented by the Bloomberg Barclays Intermediate U.S. Government/Credit Index).
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Blended Balanced Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY EQUITY AND INCOME FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 8.38% for the quarter ended December 31, 2011, and the lowest quarterly return was -7.92% for the quarter ended December 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2011
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 8.38%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (7.92%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only and after-tax returns for Institutional Class shares will vary. 
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Blended Balanced Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy Equity and Income Fund | Blended Balanced Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Blended Balanced Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 21.30%
5 Years rr_AverageAnnualReturnYear05 8.17%
10 Years rr_AverageAnnualReturnYear10 9.47%
Hennessy Equity and Income Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Equity and Income Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HEIFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.41%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.51%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.09% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.55%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 158
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 490
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,845
Annual Return 2010 rr_AnnualReturn2010 11.34%
Annual Return 2011 rr_AnnualReturn2011 10.61%
Annual Return 2012 rr_AnnualReturn2012 8.82%
Annual Return 2013 rr_AnnualReturn2013 15.03%
Annual Return 2014 rr_AnnualReturn2014 11.26%
Annual Return 2015 rr_AnnualReturn2015 (2.62%)
Annual Return 2016 rr_AnnualReturn2016 5.73%
Annual Return 2017 rr_AnnualReturn2017 13.51%
Annual Return 2018 rr_AnnualReturn2018 (4.33%)
Annual Return 2019 rr_AnnualReturn2019 15.99%
Label rr_AverageAnnualReturnLabel Hennessy Equity and Income Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 15.99%
5 Years rr_AverageAnnualReturnYear05 5.34%
10 Years rr_AverageAnnualReturnYear10 8.32%
Hennessy Equity and Income Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Equity and Income Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 13.96%
5 Years rr_AverageAnnualReturnYear05 3.66%
10 Years rr_AverageAnnualReturnYear10 7.06%
Hennessy Equity and Income Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Equity and Income Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 10.87%
5 Years rr_AverageAnnualReturnYear05 3.99%
10 Years rr_AverageAnnualReturnYear10 6.61%
Hennessy Equity and Income Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HEIIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.29%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.09% [2]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.18%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 120
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 375
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 649
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,432
Label rr_AverageAnnualReturnLabel Hennessy Equity and Income Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 16.50%
5 Years rr_AverageAnnualReturnYear05 5.75%
10 Years rr_AverageAnnualReturnYear10 8.66%
Hennessy Balanced Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY BALANCED FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Balanced Fund seeks a combination of capital appreciation and current income.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 52% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 52.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests approximately 50% of its assets in roughly equal dollar amounts in the 10 highest dividend-yielding Dow Jones Industrial Average (“DJIA”) stocks (known as the “Dogs of the Dow”), but limits exposure to market risk and volatility by investing approximately 50% of its assets in U.S. Treasury securities with a maturity of less than one year.
The total portfolio is divided into multiple sub-portfolios, each of which uses the Dogs of the Dow strategy. On various dates throughout the year, each of these sub-portfolios is reviewed. In a review, the Investment Manager determines the 10 highest yielding common stocks in the DJIA by annualizing the last quarterly or semi-annual ordinary dividend declared on each stock and dividing the result by the market value of that stock. The Fund then purchases those stocks in approximately equal amounts for the sub-portfolio being reviewed. From time to time, the Fund also may purchase an approximately equal amount of U.S. Treasury securities having a remaining maturity of less than one year for the sub-portfolio being reviewed. On the next date, another sub-portfolio is reviewed in a similar manner.
Regardless of whether they remain in the DJIA or retain the characteristics of Dogs of the Dow stocks, the Fund generally holds the stock investments within each sub-portfolio for one year, at which time the applicable sub-portfolio is up for another review. At the end of the one-year period, the Fund sells any stocks in the applicable sub-portfolio that are no longer Dogs of the Dow stocks and replaces them with stocks that are Dogs of the Dow stocks. Additionally, the Fund may sell a portion of the stocks that remain in the applicable sub-portfolio so that the rebalanced portion of the sub-portfolio adheres to the Fund’s asset allocation strategy.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
Although approximately 50% of the Fund’s portfolio is invested in U.S. Treasury securities, there are market and investment risks associated with an investment in the Fund, as there are with any security. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Formula Investing Risk: The Fund will adhere to its strategy during the course of the year, subject to applicable Securities and Exchange Commission requirements and federal tax requirements relating to mutual funds, regardless of any adverse developments that may arise. This could result in substantial losses to the Fund if, for example, the stocks selected for the Fund’s portfolio in a given year are experiencing financial difficulty or are out of favor with investors.
Non-Diversification Risk: The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Hennessy Balanced Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the DJIA, as well as an additional index that reflects the types of securities in which the Fund invests, the 50/50 Blended DJIA/Treasury Index (which consists of 50% common stocks represented by the DJIA and 50% short-duration Treasury securities represented by the ICE BofAML 1-Year Treasury Note Index).  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the Hennessy Balanced Fund, a series of The Hennessy Funds, Inc. (the “Predecessor Balanced Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Balanced Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Hennessy Balanced Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the DJIA, as well as an additional index that reflects the types of securities in which the Fund invests, the 50/50 Blended DJIA/Treasury Index (which consists of 50% common stocks represented by the DJIA and 50% short-duration Treasury securities represented by the ICE BofAML 1-Year Treasury Note Index).
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the 50/50 Blended DJIA/Treasury Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY BALANCED FUND CALENDAR YEAR TOTAL RETURNS
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown on the bar chart, the Fund’s highest quarterly return was 8.35% for the quarter ended September 30, 2010, and the lowest quarterly return was -4.24% for the quarter ended June 30, 2010.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 8.35%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (4.24%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the 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 Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the 50/50 Blended DJIA/Treasury Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the 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 Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy Balanced Fund | 50/50 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel 50/50 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 13.85%
5 Years rr_AverageAnnualReturnYear05 6.98%
10 Years rr_AverageAnnualReturnYear10 7.14%
Hennessy Balanced Fund | Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 25.34%
5 Years rr_AverageAnnualReturnYear05 12.59%
10 Years rr_AverageAnnualReturnYear10 13.40%
Hennessy Balanced Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HBFBX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.60%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 1.04% [3]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 1.14%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.89%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 192
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 594
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,021
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,212
Annual Return 2010 rr_AnnualReturn2010 8.17%
Annual Return 2011 rr_AnnualReturn2011 6.90%
Annual Return 2012 rr_AnnualReturn2012 3.73%
Annual Return 2013 rr_AnnualReturn2013 11.73%
Annual Return 2014 rr_AnnualReturn2014 2.64%
Annual Return 2015 rr_AnnualReturn2015 (0.26%)
Annual Return 2016 rr_AnnualReturn2016 9.15%
Annual Return 2017 rr_AnnualReturn2017 8.35%
Annual Return 2018 rr_AnnualReturn2018 0.10%
Annual Return 2019 rr_AnnualReturn2019 9.69%
Label rr_AverageAnnualReturnLabel Hennessy Balanced Fund Return before taxes
1 Year rr_AverageAnnualReturnYear01 9.69%
5 Years rr_AverageAnnualReturnYear05 5.31%
10 Years rr_AverageAnnualReturnYear10 5.94%
Hennessy Balanced Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Balanced Fund Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 8.37%
5 Years rr_AverageAnnualReturnYear05 3.95%
10 Years rr_AverageAnnualReturnYear10 5.03%
Hennessy Balanced Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Balanced Fund Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 6.65%
5 Years rr_AverageAnnualReturnYear05 4.02%
10 Years rr_AverageAnnualReturnYear10 4.68%
Hennessy BP Energy Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY BP ENERGY FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy BP Energy Fund seeks total return.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 87% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 87.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in companies operating in the United States in a capacity related to the supply, transportation, production, transmission, or demand of energy, also known as the energy value chain. Primary categories of the energy value chain include the following:
•
Energy Companies (Supply-side oriented) – Companies across the energy supply chain spectrum, including upstream, midstream, and downstream energy companies of various energy sources such as natural gas, crude oil, refined products, coal, and electricity, as well as companies that provide services to oil and gas companies.
•
Industrial Companies – Energy-intensive chemical, metal, industrial, and manufacturing companies and engineering and construction companies that the Portfolio Managers expect to benefit from growing U.S. energy production and lower feedstock costs relative to global costs.
•
Infrastructure Companies – Companies that design, manufacture, install, own, operate, or service equipment or assets that enable the connectivity of energy supply and demand or provide technology and engineering solutions to industrial, commercial, and consumer markets. Examples include (1) a manufacturer of liquefied natural gas products for locomotives powered by natural gas, (2) a manufacturer of engines that primarily use natural gas and alternative fuels to power school buses and refuse collection trucks, and (3) a specialty energy infrastructure contractor that provides engineering, procurement, and construction services to the oil, gas, refinery, petrochemical, and power industries.
•
Transportation and Logistics Companies – Companies that provide solutions for transportation and logistics to the U.S. manufacturing industry, such as trucking, railroads, and airlines. 
The Fund invests primarily in common stocks and invests without regard to market capitalization. The Fund may also invest up to 25% of its total assets in securities of energy-related master limited partnerships (“MLPs”).
In addition to the principal strategies discussed above, the Fund may also invest in preferred stocks, warrants, options, equity-like instruments, and debt instruments. Furthermore,  the Fund may invest up to 25% of its total assets in high-quality debt securities, preferred stock, and convertible securities of energy renaissance companies, except that with respect to up to 10% of its total assets the Fund may invest in high-yield debt securities, preferred shares, and convertible securities (commonly referred to as “junk securities”). Energy renaissance companies are companies operating in a capacity related to the supply, transportation, storage, refining and intense end use of energy, which can also be described as companies operating across the entire spectrum of the energy value chain.
The Portfolio Managers use a proprietary research and investment process that involves fundamental and quantitative analysis of various macroeconomic and commodity price and other factors to select the Fund’s investments and determine the weighting of each investment. The Portfolio Managers may sell all or a portion of a position of the Fund’s portfolio holding for a number of reasons, including (1) the issuer’s fundamentals deteriorating, (2) the parameters established for the security’s profits or losses being realized, or (3) the Fund requiring cash to meet redemption requests.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Cash Flow Risk: The Fund expects that a substantial portion of the cash flow it receives will be derived from its investments in MLPs. The amount and tax characterization of cash available for distribution by such companies depends upon the amount of cash generated by the such companies’ operations. Cash available for distribution may vary widely from quarter to quarter and will be affected by various factors affecting each company’s operations. The Fund periodically will distribute more than its income and net realized capital gains, which means a portion of each shareholder’s distribution would be a return of capital. A return of capital distribution reduces the basis of a shareholder’s shares so the shareholder may be required to recognize a capital gain when the shareholder sells shares.
Industry Concentration Risk: The Fund concentrates its investments in the energy industry, and its performance is therefore tied closely to, and affected by, industry developments. Energy companies may be adversely affected by fluctuations in commodity prices, reduced supply or demand of energy commodities, the disruption of energy supplies transported on interstate pipelines, depletion of reserves, extreme weather or environmental hazards, accidents or other operating issues, changes in the regulatory environment, slowdowns in new construction, rising interest rates, and terrorist threats on energy assets.
Liquidity Risk: The Fund may not be able to sell some or all of the investments that it holds due to a lack of demand in the marketplace or other factors such as market turmoil, or the Fund may be forced to sell an illiquid asset to meet redemption requests or other cash needs and may only be able to sell those investments at a loss. Illiquid assets may also be difficult to value.
MLP Risk: Investment in securities of an MLP involves risks that differ from investments in common stock, including risks related to limited control and limited rights to vote on matters affecting the MLP, risks related to potential conflicts of interest between the MLP and the MLP’s general partner, cash flow risks, dilution risks, and risks related to the general partner’s right to require unitholders to sell their common units at an undesirable time or price. Certain MLP securities may trade in lower volumes due to their smaller capitalizations. Accordingly, those MLPs may be subject to more abrupt or erratic price movements and may lack sufficient market liquidity to enable the Fund to effect sales at an advantageous time or without a substantial drop in price. MLPs are generally considered interest-rate sensitive investments. During periods when interest rates are rising, these investments may not provide attractive returns. If the Fund holds an MLP until its cost basis for tax purposes is reduced to zero, subsequent distributions received by the Fund will be taxed at ordinary income rates, and a shareholder may receive a corrected Form 1099.
MLP Tax Risk: A change in current tax law, or a change in the business of a given MLP, could result in an MLP being treated as a corporation or other form of taxable entity for U.S. federal income tax purposes. This would require the MLP to pay U.S. federal income tax, excise tax, or another form of tax on its taxable income, thereby reducing the amount of cash available for distribution by the MLP and potentially causing any distributions received by the Fund to be taxed as dividend income, return of capital, or capital gain. Therefore, if any MLPs owned by the Fund were treated as corporations or other forms of taxable entity for U.S. federal income tax purposes, the after-tax return to the Fund with respect to its investment in such MLPs could be materially reduced, which could cause a material decrease in the net asset value per share of the Fund’s shares. If the Fund holds an MLP until its cost basis for tax purposes is reduced to zero, subsequent distributions received by the Fund are taxed at ordinary income rates, and a shareholder may receive a corrected Form 1099. Furthermore, because the MLP itself does not pay federal income tax, its income or loss is allocated to its shareholders, including the Fund, regardless of whether the shareholders receive any cash payment from the MLP.
RIC Qualification Risk: To qualify for treatment as a regulated investment company (“RIC”) under the Internal Revenue Code (the “Code”), the Fund must meet certain income source, asset diversification, and annual distribution requirements. The Fund’s MLP investments may make it more difficult for the Fund to meet these requirements. The asset diversification requirements include a requirement that, at the end of each quarter of each taxable year, not more than 25% of the value of the Fund’s total assets is invested in the securities (including debt securities) of one or more qualified publicly traded partnerships. The Fund anticipates that the MLPs in which it invests will be qualified publicly traded partnerships. If the Fund’s MLP investments exceed this 25% limitation, which could occur if the Fund’s investment in an MLP affiliate were recharacterized as an investment in an MLP, then the Fund would not satisfy the diversification requirements and could fail to qualify as a RIC. If, in any year, the Fund fails to qualify as a RIC for any reason, the Fund would be taxed as a corporation and would become subject to corporate income tax. The resulting corporate taxes could substantially reduce the Fund’s net assets, the amount of income available for distribution, and the amount of the Fund’s distributions.
Temporary Defensive Positions Risk: From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political conditions. To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective. For temporary defensive purposes, the Fund may invest in cash or short-term obligations.
Small-Sized and Medium-Sized Companies Risk: The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one and five years and since inception compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the S&P 500® Energy Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the BP Capital TwinLine Energy Fund, a series of Professionally Managed Portfolios (the “Predecessor BP TwinLine Energy Fund”), pursuant to a reorganization that took place on October 26, 2018. The performance information provided for the periods on or prior to October 26, 2018, is historical information for the Predecessor BP TwinLine Energy Fund. The Predecessor BP TwinLine Energy Fund was managed by BP Capital Fund Advisors, LLC, and had a substantially similar investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one and five years and since inception compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the S&P 500® Energy Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the S&P 500® Energy Index as an additional index to compare the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY BP ENERGY FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 17.09% for the quarter ended March 31, 2019, and the lowest quarterly return was -32.57% for the quarter ended December 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 17.09%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (32.57%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated federal 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns before taxes” or “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the S&P 500® Energy Index as an additional index to compare the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns before taxes” or “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy BP Energy Fund | S&P 500® Energy Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel S&P 500® Energy Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 11.82%
5 Years rr_AverageAnnualReturnYear05 (1.85%)
Since Inception rr_AverageAnnualReturnSinceInception (2.87%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy BP Energy Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
Since Inception rr_AverageAnnualReturnSinceInception 12.03%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy BP Energy Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HNRGX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.48% [4]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.58%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.98%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 201
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 621
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,068
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,306
Annual Return 2014 rr_AnnualReturn2014 (1.75%)
Annual Return 2015 rr_AnnualReturn2015 (24.67%)
Annual Return 2016 rr_AnnualReturn2016 42.96%
Annual Return 2017 rr_AnnualReturn2017 1.89%
Annual Return 2018 rr_AnnualReturn2018 (31.16%)
Annual Return 2019 rr_AnnualReturn2019 5.74%
Label rr_AverageAnnualReturnLabel Hennessy BP Energy Fund - Investor Returns before taxes [5]
1 Year rr_AverageAnnualReturnYear01 5.74% [5]
5 Years rr_AverageAnnualReturnYear05 (4.39%) [5]
Since Inception rr_AverageAnnualReturnSinceInception (3.96%) [5]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013 [5]
Hennessy BP Energy Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy BP Energy Fund - Investor Return after taxes on distributions [5]
1 Year rr_AverageAnnualReturnYear01 5.74% [5]
5 Years rr_AverageAnnualReturnYear05 (4.39%) [5]
Since Inception rr_AverageAnnualReturnSinceInception (4.12%) [5]
Hennessy BP Energy Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy BP Energy Fund - Investor Return after taxes on distributions and sale of Fund shares [5]
1 Year rr_AverageAnnualReturnYear01 3.40% [5]
5 Years rr_AverageAnnualReturnYear05 (3.27%) [5]
Since Inception rr_AverageAnnualReturnSinceInception (2.99%) [5]
Hennessy BP Energy Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HNRIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.25%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.42% [4]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.42%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.67%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 170
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 526
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 907
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,976
Label rr_AverageAnnualReturnLabel Hennessy BP Energy Fund - Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 6.05%
5 Years rr_AverageAnnualReturnYear05 (4.11%)
Since Inception rr_AverageAnnualReturnSinceInception (3.72%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy BP Midstream Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY BP MIDSTREAM FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy BP Midstream Fund seeks capital appreciation through distribution growth and current income.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 02/28/2021
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 41% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 41.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of this 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in midstream energy infrastructure companies. An issuer is considered to be a midstream energy infrastructure company if it owns and operates assets used in energy logistics, including, without limitation, assets used in transporting, storing, gathering, processing, distributing, or marketing of natural gas, natural gas liquids, crude oil, refined products, coal, or electricity, or provides energy-related equipment and services. The Fund invests primarily in master limited partnerships (“MLPs”) and common stocks without regard to market capitalization.  In addition to the aforementioned principal strategies, the Fund may also invest in preferred stocks, warrants, options, equity-like instruments, and debt instruments.
In selecting investments for the Fund, the Portfolio Managers combine a top-down deductive reasoning approach with a detailed bottom-up analysis of individual companies that have exposure to the trends identified. The Portfolio Managers may sell all or a portion of a position of the Fund’s portfolio holding for a number of reasons, including (1) the issuer’s fundamentals deteriorating, (2) the parameters established for the security’s profits or losses being realized, or (3) the Fund requiring cash to meet redemption requests.
The Fund is non-diversified under the Investment Company Act and under Subchapter M of the Code. Accordingly, the Fund typically invests a greater portion of its assets, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. In addition, as a “C” corporation, the Fund generally will be subject to U.S. federal income tax on its taxable income at the tax rate applicable to corporations (currently 21%), will not benefit from current favorable federal income tax rates on long-term capital gains, and will be subject to state and local income taxes by reason of its investments in equity securities of MLPs.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Cash Flow Risk: The Fund expects that a substantial portion of the cash flow it receives will be derived from its investments in MLPs. The amount and tax characterization of cash available for distribution by such companies depends upon the amount of cash generated by such companies’ operations. Cash available for distribution may vary widely from quarter to quarter and will be affected by various factors affecting each company’s operations. The Fund periodically will distribute more than its income and net realized capital gains, which means a portion of a shareholder’s distribution would be a return of capital. A return of capital distribution reduces the basis of a shareholder’s shares so a shareholder may be required to recognize a capital gain when the shareholder sells shares.
Dividend Distribution Risk: The Fund’s dividend distribution policy is intended to provide consistent distributions to its shareholders at a rate that over time is similar to the distribution rate the Fund receives from the companies in which it invests, without offset for the expenses of the Fund. The amount of the Fund’s distributions is based on, among other considerations, cash and stock distributions the Fund actually receives from portfolio investments, including returns of capital and any special cash payments received to offset distribution reductions resulting from restructurings. Furthermore, the Fund’s total distribution payment amount may be derived from net income, net profit from the sale of securities, or other capital sources (the latter of which represents a return of capital). A return of capital occurs when some or all of the money that a shareholder invested in the Fund is paid back to the shareholder. A return of capital distribution does not necessarily reflect the Fund’s investment performance and should not be confused with “yield” or “income.” Shareholders should not draw any conclusions about the Fund’s investment performance from the amounts of these distributions. For certain securities held by the Fund, such as MLP units, the percentages attributed to each category (net income, net profit from sale, and other capital sources) are estimated using historical information because the character of the amounts received from such entities is unknown until after the end of the calendar year.
Industry Concentration Risk: The Fund concentrates its investments in the energy industry, and its performance is therefore tied closely to, and affected by, industry developments. Energy companies may be adversely affected by fluctuations in commodity prices, reduced supply or demand of energy commodities, the disruption of energy supplies transported on interstate pipelines, depletion of reserves, extreme weather or environmental hazards, accidents or other operating issues, changes in the regulatory environment, slowdowns in new construction, rising interest rates, and terrorist threats on energy assets.
Liquidity Risk: MLP common units and equity securities of MLP affiliates, including I-Shares, often trade on national securities exchanges. However, certain securities, including those of issuers with smaller capitalizations, may trade less frequently. The market movements of such securities with limited trading volumes may be more abrupt or erratic than those with higher trading volumes. As a result of the limited liquidity of such securities, the Fund could have greater difficulty selling such securities at the time and price that the Fund would like. This may also adversely affect the Fund’s ability to remit dividend payments to shareholders.
MLP Risk: Investments in securities of an MLP involve risks that differ from investments in common stock, including risks related to limited control and limited rights to vote on matters affecting the MLP, risks related to potential conflicts of interest between the MLP and the MLP’s general partner, cash flow risks, dilution risks, and risks related to the general partner’s right to require unit-holders to sell their common units at an undesirable time or price. Certain MLP securities may trade in lower volumes due to their smaller capitalizations. Accordingly, those MLPs may be subject to more abrupt or erratic price movements and may lack sufficient market liquidity to enable the Fund to effect sales at an advantageous time or without a substantial drop in price. MLPs are generally considered interest-rate sensitive investments. During periods when interest rates are rising, these investments may not provide attractive returns.
Non-Diversification Risk: The Fund is non-diversified under the Investment Company Act and employs a concentrated investment strategy. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified, less concentrated fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Temporary Defensive Positions Risk: From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political other conditions. To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective. For temporary defensive purposes, the Fund may invest in cash or short-term obligations.
Medium-Sized Company Risk: The Fund invests in medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies.
Tax Risks: Tax risks associated with investments in the Fund include, but are not limited to, the following:
Fund Structure Risk. Unlike most open-end mutual funds that are structured as regulated investment companies for U.S. federal income tax purposes and unlike entities treated as partnerships for tax purposes, the Fund will be taxable as a regular corporation, or “C” corporation, for U.S. federal income tax purposes. This means the Fund generally will be subject to U.S. federal income tax on its taxable income at the tax rate applicable to corporations (currently 21%), will not benefit from current favorable federal income tax rates on long-term capital gains, and will be subject to state and local income taxes by reason of its investments in equity securities of MLPs. Fund income and losses will not be passed through to shareholders.
MLP Tax Risk. A change in current tax law, or a change in the business of a given MLP, could result in an MLP being treated as a corporation or other form of taxable entity for U.S. federal income tax purposes. This would require the MLP to pay U.S. federal income tax, excise tax, or another form of tax on its taxable income, thereby reducing the amount of cash available for distribution by the MLP and potentially causing any distributions received by the Fund to be taxed as dividend income, return of capital, or capital gain. Therefore, if any of the MLPs owned by the Fund were treated as corporations or other form of taxable entity for U.S. federal income tax purposes, the after-tax return to the Fund with respect to its investment in such MLPs could be materially reduced, which could cause a material decrease in the net asset value of the Fund’s shares. If the Fund holds an MLP until its cost basis for tax purposes is reduced to zero, subsequent distributions received by the Fund are taxed at ordinary income rates, and a shareholder may receive a corrected Form 1099. Furthermore, because the MLP itself does not pay federal income tax, its income or loss is allocated to its shareholders, including the Fund, regardless of whether the shareholders receive any cash payment from the MLP.
Tax Estimation/NAV Risk. In calculating the Fund’s net asset value, the Fund will account for its current taxes and deferred tax liability or asset balances. The Fund will accrue a deferred income tax liability balance, at the then-effective statutory U.S. federal income tax rate (currently 21%) plus an estimated state and local income tax rate, for its future tax liability associated with the capital appreciation of its investments and the distributions received by the Fund from the companies in which it invests that are considered to be return of capital and for any net operating gains. Any deferred tax liability balance reduces the Fund’s net asset value. The Fund may also accrue a deferred tax asset balance, which reflects an estimate of the Fund’s future tax benefit associated with net operating losses and unrealized losses. Any deferred tax asset balance will increase the Fund’s net asset value.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act and employs a concentrated investment strategy. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified, less concentrated fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one and five years and since inception compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Alerian MLP Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus. The Fund is the successor to the BP Capital TwinLine MLP Fund, a series of Professionally Managed Portfolios (the “Predecessor BP TwinLine MLP Fund”), pursuant to a reorganization that took place on October 26, 2018. The performance information provided for the periods on or prior to October 26, 2018, is historical information for the Predecessor BP TwinLine MLP Fund. The Predecessor BP TwinLine MLP Fund was managed by BP Capital Fund Advisors, LLC and had a substantially similar investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance. Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one and five years and since inception compare with those of an index that reflects a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Alerian MLP Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Alerian MLP Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY BP MIDSTREAM FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 20.27% for the quarter ended June 30, 2016, and the lowest quarterly return was -26.04% for the quarter ended September 30, 2015.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 20.27%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2015
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.04%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated federal 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “returns after taxes on distributions and sale of Fund shares” may be higher than its “returns before taxes” or “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Alerian MLP Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. The Fund’s “returns after taxes on distributions and sale of Fund shares” may be higher than its “returns before taxes” or “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Hennessy BP Midstream Fund | Alerian MLP Index (reflects no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Alerian MLP Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 6.56%
5 Years rr_AverageAnnualReturnYear05 (7.00%)
Since Inception rr_AverageAnnualReturnSinceInception (5.13%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy BP Midstream Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
Since Inception rr_AverageAnnualReturnSinceInception 12.03%
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy BP Midstream Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HMSFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.10%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.03% [6]
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.57%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.64%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.89%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.13%) [7]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.76%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 179
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 581
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,009
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,201
Annual Return 2014 rr_AnnualReturn2014 11.55%
Annual Return 2015 rr_AnnualReturn2015 (28.17%)
Annual Return 2016 rr_AnnualReturn2016 21.55%
Annual Return 2017 rr_AnnualReturn2017 (4.97%)
Annual Return 2018 rr_AnnualReturn2018 (21.20%)
Annual Return 2019 rr_AnnualReturn2019 11.76%
Label rr_AverageAnnualReturnLabel Hennessy BP Midstream Fund - Investor Returns before taxes [8]
1 Year rr_AverageAnnualReturnYear01 11.76% [8]
5 Years rr_AverageAnnualReturnYear05 (6.08%) [8]
Since Inception rr_AverageAnnualReturnSinceInception (3.35%) [8]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013 [8]
Hennessy BP Midstream Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy BP Midstream Fund - Investor Return after taxes on distributions [8]
1 Year rr_AverageAnnualReturnYear01 11.76% [8]
5 Years rr_AverageAnnualReturnYear05 (6.15%) [8]
Since Inception rr_AverageAnnualReturnSinceInception (3.41%) [8]
Hennessy BP Midstream Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy BP Midstream Fund - Investor Return after taxes on distributions and sale of Fund shares [8]
1 Year rr_AverageAnnualReturnYear01 6.96% [8]
5 Years rr_AverageAnnualReturnYear05 (4.52%) [8]
Since Inception rr_AverageAnnualReturnSinceInception (2.52%) [8]
Hennessy BP Midstream Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HMSIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 1.10%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component2 Other Expenses rr_Component2OtherExpensesOverAssets 0.03% [6]
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.49%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.46%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.56%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (0.05%) [7]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.51%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 154
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 488
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 845
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,852
Label rr_AverageAnnualReturnLabel Hennessy BP Midstream Fund - Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 11.96%
5 Years rr_AverageAnnualReturnYear05 (5.85%)
Since Inception rr_AverageAnnualReturnSinceInception (3.11%)
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2013
Hennessy Gas Utility Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY GAS UTILITY FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Gas Utility Fund seeks income and capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 12% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 12.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund may invest in any company whose securities are listed on a U.S. national securities exchange and in any foreign company through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar denominated securities of foreign issuers listed on U.S. national securities exchanges.  The Fund intends to provide investment results that replicate the performance of the American Gas Association Stock Index (the “AGA Stock Index”).  The AGA Stock Index is maintained by the American Gas Association, a national trade association of natural gas distribution companies, and is licensed exclusively to the Investment Manager for use as an investment strategy. The AGA Stock Index consists of all publicly traded member companies of the American Gas Association, which include natural gas distribution, gas pipeline, diversified gas, and combination gas and electric companies.  The stocks included in the Fund are chosen solely on the basis of their inclusion in the AGA Stock Index.
Under normal circumstances, the Fund intends to invest at least 85% of its net assets in the common stock of companies that have natural gas distribution and transmission operations, and no attempt is made to actively manage the Fund’s portfolio by using economic, financial, or market analysis.  The adverse financial situation of a company will not result in its elimination from the Fund’s portfolio unless the company is removed from the AGA Stock Index.  The percentage of the Fund’s assets invested in the stock of a particular company is approximately the same as the percentage weighting of such company in the AGA Stock Index.  The percentage weighting of each company in the AGA Stock Index is an amount equal to such company’s market capitalization multiplied by the percentage of such company’s assets devoted to natural gas distribution and transmission.  The latter component of this calculation is used to recognize the natural gas distribution and transmission component of the company’s asset base.
There is no predetermined acceptable range of the difference between the total return of the AGA Stock Index and the total return of the Fund.  Any difference is likely the result of various expenses incurred by the Fund, such as management fees, transaction costs, and other operating expenses, as well as subscription and redemption activity.  On the other hand, the Fund does attempt to achieve a correlation of monthly returns with the AGA Stock Index of approximately 95% or better.  A correlation of 100% would mean the total return of the Fund’s assets would increase and decrease at exactly the same rate as the total return of the AGA Stock Index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with an investment in the Fund. The value of an investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk:  The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Industry Concentration Risk: The Fund concentrates its investments in the natural gas and transmission industry, and its performance is therefore tied closely to, and affected by, industry developments. Natural gas companies may be adversely affected by fluctuations in natural gas prices, reduced supply or demand of natural gas, the disruption of natural gas supplies transported on interstate pipelines, depletion of reserves, extreme weather or environmental hazards, accidents or other operating issues, changes in the regulatory environment, slowdowns in new construction, rising interest rates, and terrorist threats on natural gas assets.
Foreign Securities Risk:  The Fund may invest in foreign companies.  There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies.  Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes in the foreign country.  Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
Index Tracking Risk:  While the Fund seeks to track the performance of the AGA Stock Index as closely as possible, the Fund’s return may not always be able to match or achieve a high correlation due to factors such as the expenses incurred by the Fund, such as management fees, transaction costs, and other operating expenses, that are not incurred by the AGA Stock Index and the possibility that the Fund may experience significant subscriptions or redemptions.  In addition, the Fund may not be fully invested at all times as a result of cash flows into the Fund or reserves of cash that are maintained in order to cover operating expenses and meet redemption requests.
Risk Lose Money [Text] rr_RiskLoseMoney The value of an investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index reflecting a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the AGA Stock Index.  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the FBR Gas Utility Index Fund (the “Predecessor Gas Utility Fund”).  The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Gas Utility Fund, which had the same investment objective and same investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future.  Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index reflecting a broad measure of market performance, the S&P 500® Index, as well as an additional index that reflects the market sector in which the Fund invests, the AGA Stock Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the AGA Stock Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund. The AGA Stock Index is calculated monthly and provided by the American Gas Association.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY GAS UTILITY FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 14.07% for the quarter ended March 31, 2019, and the lowest quarterly return was -6.60% for the quarter ended March 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 14.07%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.60%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the AGA Stock Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund. The AGA Stock Index is calculated monthly and provided by the American Gas Association.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. The Fund’s “return after taxes on distributions and sale of Fund shares” may be higher than its “returns after taxes on distributions” because it may include a tax benefit due to the capital losses generated by the sale of Fund shares.
The inception date of the Fund’s Institutional Class shares is March 1, 2017. Performance shown prior to the inception of Institutional Class shares reflects the performance of the Fund’s Investor Class shares and includes expenses that are not applicable to, and are higher than, the Fund’s Institutional Class shares.
Hennessy Gas Utility Fund | AGA Stock Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel AGA Stock Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 22.66%
5 Years rr_AverageAnnualReturnYear05 6.15%
10 Years rr_AverageAnnualReturnYear10 12.22%
Hennessy Gas Utility Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Gas Utility Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol GASFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.40%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.35%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.45%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 318
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 552
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,225
Annual Return 2010 rr_AnnualReturn2010 12.40%
Annual Return 2011 rr_AnnualReturn2011 25.15%
Annual Return 2012 rr_AnnualReturn2012 7.45%
Annual Return 2013 rr_AnnualReturn2013 25.42%
Annual Return 2014 rr_AnnualReturn2014 21.20%
Annual Return 2015 rr_AnnualReturn2015 (16.01%)
Annual Return 2016 rr_AnnualReturn2016 20.70%
Annual Return 2017 rr_AnnualReturn2017 7.03%
Annual Return 2018 rr_AnnualReturn2018 (3.51%)
Annual Return 2019 rr_AnnualReturn2019 20.78%
Label rr_AverageAnnualReturnLabel Hennessy Gas Utility Fund - Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 20.78%
5 Years rr_AverageAnnualReturnYear05 4.81%
10 Years rr_AverageAnnualReturnYear10 11.26%
Hennessy Gas Utility Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Gas Utility Fund - Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 18.78%
5 Years rr_AverageAnnualReturnYear05 3.35%
10 Years rr_AverageAnnualReturnYear10 9.98%
Hennessy Gas Utility Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Gas Utility Fund - Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 13.63%
5 Years rr_AverageAnnualReturnYear05 3.57%
10 Years rr_AverageAnnualReturnYear10 9.14%
Hennessy Gas Utility Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HGASX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.40%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.29%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.29%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.69%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 70
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 221
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 384
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 859
Label rr_AverageAnnualReturnLabel Hennessy Gas Utility Fund - Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 21.18%
5 Years rr_AverageAnnualReturnYear05 5.01%
10 Years rr_AverageAnnualReturnYear10 11.37%
Hennessy Japan Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY JAPAN FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Japan Fund seeks long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 9% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 9.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of Japanese companies.  The Fund considers a Japanese company to be a company organized under the laws of Japan, for which the principal securities trading market is Japan, or that has a majority of its assets or business in Japan.  The Fund’s equity investments may include common stocks, preferred stocks, warrants and other rights, and securities convertible into or exchangeable for common stocks, such as convertible bonds. The Fund’s investments also may include investments in Japan real estate investment trusts or other investment companies (including exchange-traded funds, referred to as ETFs) that invest in equity securities of Japanese companies.  The Fund invests in companies regardless of market capitalization. As of January 31, 2020, the average market capitalization of the stocks held by the Fund was $34.1 billion.
While the Fund is considered a diversified mutual fund, it employs a relatively concentrated investment strategy and may hold securities of fewer issuers than other diversified funds.
Using in-depth analysis and on-site research, the Portfolio Managers focus on stocks with a potential “value gap” by screening for companies that they identify as having strong businesses and management, trading at an attractive price.  The Portfolio Managers limit the portfolio to what they consider to be their best ideas and maintain a concentrated number of holdings. The Portfolio Managers typically sell an investment when the reasons for buying it no longer apply, such as when they determine that a company’s prospects have changed, that a company’s stock is fully valued by the market, or that the company is beginning to show deteriorating fundamentals.  They also may sell an investment if it becomes, in their determination, too large of a position in the Fund.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with an investment in the Fund. The value of an investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk: The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Foreign Securities, Foreign Currency, and Japan-Specific Risk: There are specific risks associated with investing in the securities of foreign companies, including fluctuations in the exchange rates of foreign currencies that impact the U.S. dollar value of a security. The Fund concentrates its investments in the securities of Japanese companies, and the Fund’s performance may be affected by the social, political, and economic conditions in Japan. The Japanese economy has at times in the past been negatively affected by government intervention and protectionism, a deflationary macroeconomic environment, a heavy reliance on international trade, and natural disasters. Some of these factors, as well as a large government debt burden, an aging population, and changes to fiscal, monetary, or trade policies, may affect Japanese markets and the Fund’s performance. Japan’s international trade impacts Japan’s economic growth, and adverse economic conditions in the United States or other trading 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, and social instability in those countries.
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The Fund is currently substantially invested in the consumer discretionary, consumer staples, and industrials sectors, and its performance is therefore tied closely to, and affected by, developments in these industries. Companies in the consumer discretionary sector may be affected by commodity price volatility, consumer preferences, competition, changing demographics, and labor relations. These companies depend heavily on disposable household income and consumer spending, and social trends and marketing campaigns may significantly affect demand for their products. Consumer discretionary companies may also lose value more quickly in periods of economic downturns because their products are viewed as nonessential luxury items. Companies in the consumer staples sector may be affected by commodity production and pricing, consumer confidence, spending, and preferences, product cycles, marketing, competition, and government regulation. In particular, the success of consumer staples is often strongly affected by fads and marketing campaigns, as well as government regulations. Finally, companies in the industrials sector may be adversely affected by changes in the supply of and demand for products and services, product obsolescence, environmental liabilities, and product liability.
Small-Sized and Medium-Sized Companies Risk: The Fund may invest in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Investment Company Securities Risk: When the Fund invests in another investment company (including an ETF), it will indirectly bear its proportionate share of any fees and expenses payable directly by the other investment company. Therefore, the Fund will incur higher expenses, many of which may be duplicative. In addition, the Fund may be affected by the other investment company’s losses and the level of risk arising from its investment practices (such as the use of leverage). The Fund has no control over the risks taken by the other investment company.
ETF Risk: In addition to risks generally associated with investments in investment company securities, investments in ETFs are subject to the following additional risks that do not apply to non-ETFs: (i) an ETF’s shares may trade at a market price that is above or below their net asset value; (ii) an active trading market for an ETF’s shares may not develop or be maintained; (iii) the ETF may employ an investment strategy that utilizes high leverage ratios; and (iv) trading of an ETF’s shares may be halted if the listing exchange’s officials deem such action appropriate, the shares are de-listed from the exchange, or the activation of market-wide “circuit breakers” (which are tied to large decreases in stock prices) halts stock trading generally.
Risk Lose Money [Text] rr_RiskLoseMoney The value of an investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell/Nomura Total Market™ Index and the Tokyo Stock Price Index (TOPIX). For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the Hennessy Japan Fund, a series of Hennessy SPARX Funds Trust (the “Predecessor Japan Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Japan Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund.  The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the Russell/Nomura Total Market™ Index and the Tokyo Stock Price Index (TOPIX).
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY JAPAN FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 12.00% for the quarter ended December 31, 2010, and the lowest quarterly return was -13.88% for the quarter ended December 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2010
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 12.00%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (13.88%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the 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 Fund’s “return after taxes on distributions” may be higher than its “returns before taxes” because it may include a tax benefit due to the capital losses generated by distributions.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.  The Fund’s “return after taxes on distributions” may be higher than its “returns before taxes” because it may include a tax benefit due to the capital losses generated by distributions.
Returns are presented in U.S. dollar terms.
Hennessy Japan Fund | Russell/Nomura Total Market Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell/Nomura Total Market Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 20.07%
5 Years rr_AverageAnnualReturnYear05 8.56%
10 Years rr_AverageAnnualReturnYear10 7.20%
Hennessy Japan Fund | TOPIX (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel TOPIX (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 19.67%
5 Years rr_AverageAnnualReturnYear05 8.35%
10 Years rr_AverageAnnualReturnYear10 7.17%
Hennessy Japan Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HJPNX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.39% [9]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.49%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.44%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 147
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 456
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 787
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,724
Annual Return 2010 rr_AnnualReturn2010 20.64%
Annual Return 2011 rr_AnnualReturn2011 0.29%
Annual Return 2012 rr_AnnualReturn2012 11.61%
Annual Return 2013 rr_AnnualReturn2013 26.16%
Annual Return 2014 rr_AnnualReturn2014 6.98%
Annual Return 2015 rr_AnnualReturn2015 12.95%
Annual Return 2016 rr_AnnualReturn2016 11.26%
Annual Return 2017 rr_AnnualReturn2017 32.04%
Annual Return 2018 rr_AnnualReturn2018 (6.57%)
Annual Return 2019 rr_AnnualReturn2019 18.04%
Label rr_AverageAnnualReturnLabel Hennessy Japan Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 18.04%
5 Years rr_AverageAnnualReturnYear05 12.85%
10 Years rr_AverageAnnualReturnYear10 12.80%
Hennessy Japan Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Japan Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 18.13%
5 Years rr_AverageAnnualReturnYear05 12.89%
10 Years rr_AverageAnnualReturnYear10 12.84%
Hennessy Japan Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Japan Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 10.84%
5 Years rr_AverageAnnualReturnYear05 10.36%
10 Years rr_AverageAnnualReturnYear10 10.81%
Hennessy Japan Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HJPIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.24% [9]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.24%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.04%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 106
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 331
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 574
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,271
Label rr_AverageAnnualReturnLabel Hennessy Japan Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 18.51%
5 Years rr_AverageAnnualReturnYear05 13.26%
10 Years rr_AverageAnnualReturnYear10 13.15%
Hennessy Japan Small Cap Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY JAPAN SMALL CAP FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Japan Small Cap Fund seeks long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of smaller Japanese companies, typically considered to be companies with market capitalizations in the bottom 20% of all publicly traded Japanese companies.  As of December 31, 2019, the bottom 20% of publicly traded Japanese companies had market capitalizations below approximately 455 billion Japanese yen, or the equivalent of $4.2 billion.  This market capitalization range will vary due to market conditions.  The Fund considers a Japanese company to be a company organized under the laws of Japan, for which the principal securities trading market is Japan, or that has a majority of its assets or business in Japan. The Fund’s investments may include common stocks, preferred stocks, warrants and other rights, and securities convertible into or exchangeable for common stocks, such as convertible bonds.  The Fund’s investments also may include investments in Japan real estate investment trusts or other investment companies (including exchange-traded funds, referred to as ETFs) that invest in equity securities of Japanese companies.
Using in-depth analysis and on-site research, the Portfolio Managers focus on stocks with a potential “value gap” by screening for small-cap companies that they identify as having strong businesses and management, trading at an attractive price.  The portfolio is limited to what the Portfolio Managers consider to be their best ideas and is unconstrained by its benchmarks.  The Portfolio Managers typically sell an investment when the reasons for buying it no longer apply, such as when they determine that a company’s prospects have changed, that a company’s stock is fully valued by the market, or that the company is beginning to show deteriorating fundamentals.  They also may sell an investment if it becomes, in their determination, too large of a position in the Fund.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with an investment in the Fund. The value of an investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk:  The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets. 
Foreign Securities, Foreign Currency, and Japan-Specific Risk: There are specific risks associated with investing in the securities of foreign companies, including fluctuations in the exchange rates of foreign currencies that impact the U.S. dollar value of a security. The Fund concentrates its investments in the securities of Japanese companies, and the Fund’s performance may be affected by the social, political, and economic conditions in Japan. The Japanese economy has at times in the past been negatively affected by government intervention and protectionism,a deflationary macroeconomic environment, a heavy reliance on international trade, and natural disasters. Some of these factors, as well as a large government debt burden, an aging population, and changes to fiscal, monetary, or trade policies, may affect Japanese markets and the Fund’s performance. Japan’s international trade impacts Japan’s economic growth, and adverse economic conditions in the United States or other trading 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, and social instability in those countries. 
Industry Concentration Risk: From time to time, the Fund may concentrate its investments in one or more industry sectors. The Fund is currently substantially invested in the consumer discretionary, industrials, and technology sectors, and its performance is therefore tied closely to, and affected by, developments in these industries. Companies in the consumer discretionary sector may be affected by commodity price volatility, consumer preferences, competition, changing demographics, and labor relations. These companies depend heavily on disposable household income and consumer spending, and social trends and marketing campaigns may significantly affect demand for their products. Consumer discretionary companies may also lose value more quickly in periods of economic downturns because their products are viewed as nonessential luxury items. Companies in the industrials sector may be adversely affected by changes in the supply of and demand for products and services, product obsolescence, environmental liabilities, and product liability. Finally, technology companies face intense competition and may be subject to extensive regulatory requirements. They may have limited product lines, markets, financial resources, or personnel. The products of technology companies may face obsolescence due to rapid technological developments, frequent new product introduction, and unpredictable changes in growth rates. 
Small-Sized and Medium-Sized Companies Risk:  The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals. 
Investment Company Securities Risk:  When the Fund invests in another investment company (including an ETF), it will indirectly bear its proportionate share of any fees and expenses payable directly by the other investment company. Therefore, the Fund will incur higher expenses, many of which may be duplicative. In addition, the Fund may be affected by the other investment company’s losses and the level of risk arising from its investment practices (such as the use of leverage). The Fund has no control over the risks taken by the other investment company. 
ETF Risk: In addition to risks generally associated with investments in investment company securities, investments in ETFs are subject to the following additional risks that do not apply to non-ETFs: (i) an ETF’s shares may trade at a market price that is above or below their net asset value; (ii) an active trading market for an ETF’s shares may not develop or be maintained; (iii) the ETF may employ an investment strategy that utilizes high leverage ratios; and (iv) trading of an ETF’s shares may be halted if the listing exchange’s officials deem such action appropriate, the shares are de-listed from the exchange, or the activation of market-wide “circuit breakers” (which are tied to large decreases in stock prices) halts stock trading generally.
Risk Lose Money [Text] rr_RiskLoseMoney The value of an investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Tokyo Stock Price Index (TOPIX), as well as an additional index that reflects the types of securities in which the Fund invests, the Russell/Nomura Small Cap™ Index. For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the Hennessy Japan Small Cap Fund, a series of Hennessy SPARX Funds Trust (the “Predecessor Japan Small Cap Fund”). The performance information provided for the periods on or prior to February 28, 2014, is historical information for the Predecessor Japan Small Cap Fund, which was managed by the same investment adviser and had the same investment objective and investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future. Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Tokyo Stock Price Index (TOPIX), as well as an additional index that reflects the types of securities in which the Fund invests, the Russell/Nomura Small Cap™ Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell/Nomura Small Cap™ Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY JAPAN SMALL CAP FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 15.51% for the quarter ended March 31, 2013, and the lowest quarterly return was -15.08% for the quarter ended December 31, 2018.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2013
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.51%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2018
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (15.08%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell/Nomura Small Cap™ Index as an additional index because it compares the Fund’s performance with the returns of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.  After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. 
The inception date of the Fund’s Institutional Class shares is June 15, 2015.  Performance shown prior to the inception of Institutional Class shares reflects the performance of the Fund’s Investor Class shares and includes expenses that are not applicable to, and are higher than, those of Institutional Class shares.
Returns are presented in U.S. dollar terms.
Hennessy Japan Small Cap Fund | Russell/Nomura Small Cap™ Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell/Nomura Small Cap™ Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 18.34%
5 Years rr_AverageAnnualReturnYear05 10.29%
10 Years rr_AverageAnnualReturnYear10 9.54%
Hennessy Japan Small Cap Fund | TOPIX (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel TOPIX (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 19.67%
5 Years rr_AverageAnnualReturnYear05 8.35%
10 Years rr_AverageAnnualReturnYear10 7.17%
Hennessy Japan Small Cap Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HJPSX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.47%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.57%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.52%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 155
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 480
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 829
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,813
Annual Return 2010 rr_AnnualReturn2010 23.99%
Annual Return 2011 rr_AnnualReturn2011 (4.17%)
Annual Return 2012 rr_AnnualReturn2012 12.76%
Annual Return 2013 rr_AnnualReturn2013 33.17%
Annual Return 2014 rr_AnnualReturn2014 8.75%
Annual Return 2015 rr_AnnualReturn2015 11.59%
Annual Return 2016 rr_AnnualReturn2016 8.52%
Annual Return 2017 rr_AnnualReturn2017 49.58%
Annual Return 2018 rr_AnnualReturn2018 (12.51%)
Annual Return 2019 rr_AnnualReturn2019 19.95%
Label rr_AverageAnnualReturnLabel Hennessy Japan Small Cap Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 19.95%
5 Years rr_AverageAnnualReturnYear05 13.71%
10 Years rr_AverageAnnualReturnYear10 13.94%
Hennessy Japan Small Cap Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Japan Small Cap Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 19.78%
5 Years rr_AverageAnnualReturnYear05 13.16%
10 Years rr_AverageAnnualReturnYear10 12.20%
Hennessy Japan Small Cap Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Japan Small Cap Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 12.27%
5 Years rr_AverageAnnualReturnYear05 10.99%
10 Years rr_AverageAnnualReturnYear10 11.02%
Hennessy Japan Small Cap Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HJSIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.80%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.32%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.32%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.12%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 114
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 356
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 617
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,363
Label rr_AverageAnnualReturnLabel Hennessy Japan Small Cap Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 20.42%
5 Years rr_AverageAnnualReturnYear05 14.07%
10 Years rr_AverageAnnualReturnYear10 14.12%
Hennessy Large Cap Financial Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY LARGE CAP FINANCIAL FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Large Cap Financial Fund seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 83% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 83.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests primarily in companies listed on U.S. national securities exchanges and in foreign companies through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar denominated securities of foreign issuers listed on U.S. national securities exchanges.  The Fund’s investments consist primarily of common stocks. 
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of large-cap companies principally engaged in the business of providing financial services, including information technology companies that are primarily engaged in providing products or services to financial services companies.  An issuer is considered principally engaged in the business of providing financial services if at least 50% of its assets, gross income, or net profits are committed to, or derived from, financial services activities.  Financial services activities are activities primarily related to consumer and commercial banking, global payments, insurance, securities and investments, specialty finance, and real estate.  Investments may include mortgage banking companies, discount brokerage companies, insurance companies, consumer finance companies, payment processing companies, savings and loan associations, savings banks, leasing companies, building and loan associations, cooperative banks, commercial banks, investment companies, other depository institutions, and real estate investment trusts. The Fund considers a large-cap company to be one that has a market capitalization of $3 billion or more, measured at the time of purchase. 
When evaluating securities to purchase, the Portfolio Managers generally look for companies that have low price-to-earnings ratios and low price-to-book ratios relative to other financial services companies.  The Portfolio Managers may choose to sell a security if they believe it has reached an excessive valuation level, when the company’s specific metrics or industry fundamentals deteriorate, or if the investment process identifies a potentially superior investment idea. They may also choose to sell a position when the company’s market capitalization drops below $3 billion.
The Fund will not invest more than 5% of its total assets in the equity-related securities of any one company that derives more than 15% of its revenues from brokerage or investment management activities.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk:  The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets. 
Industry Concentration Risk: The Fund primarily invests in financial services companies, including information technology companies that concentrate in financial services, and its performance is therefore tied closely to, and affected by, industry developments. Financial services-related companies may be significantly affected by extensive regulatory requirements, changing economic conditions, availability and cost of capital, loan demand and refinancing activity, debt defaults, interest rate changes, competition, and cybersecurity threats and breaches. 
Mortgage and Real Estate Investments Risk: Because the Fund focuses on financial services companies that issue mortgages and invest in mortgage-backed securities and other real estate investments, the Fund is subject to risks associated with the real estate market. Mortgages and real estate investments are particularly sensitive to economic downturns, changes in regulations, and fluctuating interest rates. In particular, they are subject to the risk that borrowers default on their loans and the risk that borrowers prepay some or all of the principal owed to the issuer, in each case causing the investments to fail to realize expected returns. 
Temporary Defensive Positions Risk:  From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political conditions.  To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective.  For temporary defensive purposes, the Fund may invest in cash or short-term obligations. 
Medium-Sized Companies Risk:  The Fund may invest in medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. 
Non-Diversification Risk:  The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities. 
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 1000® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Russell 1000® Financial Services Index.  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the FBR Large Cap Financial Fund (the “Predecessor Large Cap Financial Fund”).  The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Large Cap Financial Fund, which had the same investment objective and substantially similar investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future.  Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 1000® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Russell 1000® Financial Services Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell 1000® Financial Services Index as an additional index because it compares the Fund’s performance with the return of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY LARGE CAP FINANCIAL FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 24.26% for the quarter ended March 31, 2012, and the lowest quarterly return was -21.49% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2012
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 24.26%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.49%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell 1000® Financial Services Index as an additional index because it compares the Fund’s performance with the return of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.  After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. 
The inception date of the Fund’s Institutional Class shares is June 15, 2015.  Performance shown prior to the inception of Institutional Class shares reflects the performance of the Fund’s Investor Class shares and includes expenses that are not applicable to, and are higher than, those of Institutional Class shares.
Hennessy Large Cap Financial Fund | Russell 1000® Financial Services Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 1000® Financial Services Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 33.76%
5 Years rr_AverageAnnualReturnYear05 11.89%
10 Years rr_AverageAnnualReturnYear10 12.86%
Hennessy Large Cap Financial Fund | Russell 1000® Index (reflects no deduction for fees, expense or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 1000® Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 31.43%
5 Years rr_AverageAnnualReturnYear05 11.48%
10 Years rr_AverageAnnualReturnYear10 13.54%
Hennessy Large Cap Financial Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HLFNX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.68% [10]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.78%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.83%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 186
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 576
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 990
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 2,148
Annual Return 2010 rr_AnnualReturn2010 7.42%
Annual Return 2011 rr_AnnualReturn2011 (18.38%)
Annual Return 2012 rr_AnnualReturn2012 27.77%
Annual Return 2013 rr_AnnualReturn2013 42.03%
Annual Return 2014 rr_AnnualReturn2014 7.85%
Annual Return 2015 rr_AnnualReturn2015 (6.11%)
Annual Return 2016 rr_AnnualReturn2016 14.96%
Annual Return 2017 rr_AnnualReturn2017 19.38%
Annual Return 2018 rr_AnnualReturn2018 (11.73%)
Annual Return 2019 rr_AnnualReturn2019 29.75%
Label rr_AverageAnnualReturnLabel Hennessy Large Cap Financial Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 29.75%
5 Years rr_AverageAnnualReturnYear05 8.10%
10 Years rr_AverageAnnualReturnYear10 9.74%
Hennessy Large Cap Financial Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Large Cap Financial Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 29.75%
5 Years rr_AverageAnnualReturnYear05 7.21%
10 Years rr_AverageAnnualReturnYear10 8.96%
Hennessy Large Cap Financial Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Large Cap Financial Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 17.61%
5 Years rr_AverageAnnualReturnYear05 6.19%
10 Years rr_AverageAnnualReturnYear10 7.84%
Hennessy Large Cap Financial Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HILFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.54% [10]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.54%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.44%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 147
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 456
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 787
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,724
Label rr_AverageAnnualReturnLabel Hennessy Large Cap Financial Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 30.21%
5 Years rr_AverageAnnualReturnYear05 8.48%
10 Years rr_AverageAnnualReturnYear10 9.93%
Hennessy Small Cap Financial Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY SMALL CAP FINANCIAL FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Small Cap Financial Fund seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 46% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 46.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below. 
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 shares of 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 you reinvest all dividends and distributions, 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 those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests primarily in companies listed on U.S. national securities exchanges and in foreign companies through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar denominated securities of foreign issuers listed on U.S. national securities exchanges.  The Fund’s investments consist primarily of common stocks.
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of small-cap companies “principally engaged” in the business of providing financial services.  An issuer is considered “principally engaged” in the business of providing financial services if at least 50% of its assets, gross income, or net profits are committed to, or derived from, financial services activities.  Financial services activities are activities primarily related to consumer and commercial banking, global payments, insurance, securities and investments, specialty finance, and real estate. Investments may include mortgage banking companies, discount brokerage companies, insurance companies, consumer finance companies, savings and loan associations, savings banks, leasing companies, building and loan associations, cooperative banks, commercial banks, investment companies, other depository institutions, companies in the information technology industries that are primarily engaged in providing products or services to the types of companies listed above, and real estate investment trusts.  The Fund considers a small-cap company to be one that has a market capitalization of less than $3 billion, measured at the time of purchase.
When evaluating securities to purchase, the Portfolio Managers generally look for companies that have low price-to-earnings ratios and low price-to-book ratios relative to other financial services companies.  The Portfolio Managers may choose to sell a security if they believe it has reached an excessive valuation level, when the company’s specific metrics or industry fundamentals deteriorate, or if the investment process identifies a potentially superior investment idea. They may also choose to sell a position when the company’s market capitalization rises above $3 billion.
The Fund will not invest more than 5% of its total assets in the equity-related securities of any one company that derives more than 15% of its revenues from brokerage or investment management activities.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk:  The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions, political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Industry Concentration Risk:  The Fund concentrates its investments in the financial services industry, and its performance is therefore closely therefore tied closely to, and affected by, industry developments. Financial services companies may be significantly affected by extensive regulatory requirements, changing economic conditions, availability and cost of capital, loan demand and refinancing activity, debt defaults, interest rate changes, competition, and cybersecurity threats and breaches. 
Mortgage and Real Estate Investments Risk: Because the Fund focuses on financial services companies that issue mortgages and invest in mortgage-backed securities and other real estate investments, the Fund is subject to risks associated with the real estate market. Mortgages and real estate investments are particularly sensitive to economic downturns, changes in regulations, and fluctuating interest rates. In particular, they are subject to the risk that borrowers default on their loans and the risk that borrowers prepay some or all of the principal owed to the issuer, in each case causing the investments to fail to realize expected returns.
Temporary Defensive Positions Risk:  From time to time, the Fund may take temporary defensive positions in response to adverse market, economic, or political conditions.  To the extent the assets of the Fund are invested in temporary defensive positions, the Fund may not achieve its investment objective.  For temporary defensive purposes, the Fund may invest in cash or short-term obligations.
Small-Sized and Medium-Sized Companies Risk: The Fund invests in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies.  Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Non-Diversification Risk:  The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The Fund is non-diversified under the Investment Company Act. Accordingly, the Fund typically invests a greater portion of its assets in, and its performance may be affected by, a smaller number of issuers than if it were a diversified fund. Further, the Fund may experience greater losses as a result of a single issuer’s unfavorable market or economic conditions or other adverse developments impacting the market value of the issuer’s securities.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 2000® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Russell 2000® Financial Services Index.  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the FBR Small Cap Financial Fund (the “Predecessor Small Cap Financial Fund”).  The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Small Cap Financial Fund, which had the same investment objective and substantially similar investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future.  Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of an index that reflects a broad measure of market performance, the Russell 2000® Index, as well as an additional index that reflects the market sector in which the Fund invests, the Russell 2000® Financial Services Index.
Performance Additional Market Index [Text] rr_PerformanceAdditionalMarketIndex We use the Russell 2000® Financial Services Index as an additional index because it compares the Fund’s performance with the return of an index reflecting the performance of investments similar to those of the Fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY SMALL CAP FINANCIAL FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 25.41% for the quarter ended December 31, 2016, and the lowest quarterly return was -21.72% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.41%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.72%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
We use the Russell 2000® Financial Services Index as an additional index because it compares the Fund’s performance with the return of an index reflecting the performance of investments similar to those of the Fund.
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary. 
Hennessy Small Cap Financial Fund | Russell 2000® Financial Services Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 2000® Financial Services Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 24.21%
5 Years rr_AverageAnnualReturnYear05 9.10%
10 Years rr_AverageAnnualReturnYear10 12.09%
Hennessy Small Cap Financial Fund | Russell 2000® Index (reflects no deductions for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Russell 2000® Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 25.52%
5 Years rr_AverageAnnualReturnYear05 8.23%
10 Years rr_AverageAnnualReturnYear10 11.83%
Hennessy Small Cap Financial Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HSFNX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.43%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.53%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01% [11]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.59%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 162
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 502
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 866
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,889
Annual Return 2010 rr_AnnualReturn2010 17.50%
Annual Return 2011 rr_AnnualReturn2011 (15.63%)
Annual Return 2012 rr_AnnualReturn2012 21.42%
Annual Return 2013 rr_AnnualReturn2013 36.59%
Annual Return 2014 rr_AnnualReturn2014 (3.40%)
Annual Return 2015 rr_AnnualReturn2015 11.74%
Annual Return 2016 rr_AnnualReturn2016 33.41%
Annual Return 2017 rr_AnnualReturn2017 (0.20%)
Annual Return 2018 rr_AnnualReturn2018 (15.86%)
Annual Return 2019 rr_AnnualReturn2019 19.88%
Label rr_AverageAnnualReturnLabel Hennessy Small Cap Financial Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 19.88%
5 Years rr_AverageAnnualReturnYear05 8.46%
10 Years rr_AverageAnnualReturnYear10 9.07%
Hennessy Small Cap Financial Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Small Cap Financial Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 18.91%
5 Years rr_AverageAnnualReturnYear05 6.62%
10 Years rr_AverageAnnualReturnYear10 7.56%
Hennessy Small Cap Financial Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Small Cap Financial Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 12.43%
5 Years rr_AverageAnnualReturnYear05 6.55%
10 Years rr_AverageAnnualReturnYear10 7.24%
Hennessy Small Cap Financial Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HISFX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.90%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 0.33%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.33%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01% [11]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 126
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 393
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 681
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,500
Label rr_AverageAnnualReturnLabel Hennessy Small Cap Financial Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 20.21%
5 Years rr_AverageAnnualReturnYear05 8.86%
10 Years rr_AverageAnnualReturnYear10 9.41%
Hennessy Technology Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading HENNESSY TECHNOLOGY FUND
Objective [Heading] rr_ObjectiveHeading Investment Objective 
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock
The Hennessy Technology Fund seeks long-term capital appreciation.
Expense [Heading] rr_ExpenseHeading Fund 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. You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples 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 02/28/2021
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 185% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 185.00%
Expense Exchange Traded Fund Commissions [Text] rr_ExpenseExchangeTradedFundCommissions You may pay other fees to financial intermediaries, such as brokerage commissions, that are not reflected in the tables and examples below.
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 shares of 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 you reinvest all dividends and distributions, that your investment has a 5% return each year, and that the Fund’s operating expenses are equal to the total annual fund operating expenses after expense reimbursement for the first year and equal to total annual fund operating expenses for the remaining years.
Expense Example by, Year, Caption [Text] rr_ExpenseExampleByYearCaption Although your actual costs may be higher or lower, based on those assumptions, your costs would be:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
The Fund invests primarily in companies listed on U.S. national securities exchanges and in foreign companies through American Depositary Receipts or other types of depositary receipts, which are U.S. dollar denominated securities of foreign issuers listed on U.S. national securities exchanges.
Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in securities of companies that are principally engaged in the research, design, development, manufacturing, or distributing of products or services in the technology industry. Potential investments include, but are not limited to, the following industries: application software, communications equipment, data processing, electronic components and manufacturing services, home entertainment software, internet and direct marketing retailers, internet software and services, IT consulting, semiconductor equipment, systems software, and technology hardware, storage, and distributors.
From a universe of stocks in the S&P Capital IQ Database with market capitalizations exceeding $175 million, the portfolio management team identifies approximately 60 common stocks (weighted equally by dollar amount) with the following attributes:
•
Sector-leading cash flows and profits
•
History of delivering returns in excess of cost of capital
•
Attractive relative valuation
•
Ability to generate cash
•
Attractive balance sheet risk profile
•
Prospects for sustainable profitability
The universe of stocks is re-screened and the portfolio is rebalanced approximately on a monthly basis.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
As with any security, there are market and investment risks associated with your investment in the Fund. The value of your investment will fluctuate over time, and it is possible to lose money. The principal risks of investing in the Fund include the following:
Market and Equity Investments Risk:  The market value of a security may move up or down, and these fluctuations may cause a security to be worth more or less than the price originally paid for it. Market risk may affect a single company, an industry, a sector of the economy, or the market as a whole. The value of equity securities will fluctuate due to many factors, including the past and predicted earnings of the issuer, the quality of the issuer’s management, general market conditions,  political and other events, forecasts for the issuer’s industry, and the value of the issuer’s assets.
Small-Sized and Medium-Sized Companies Risk:  The Fund may invest in small-sized and medium-sized companies, which may have more limited liquidity and greater price volatility than larger, more established companies. Smaller companies may have limited product lines, markets, and financial resources, and their management may be dependent on a limited number of key individuals.
Industry Concentration Risk:  The Fund concentrates its investments within the information technology sector, and its performance  is therefore tied closely to, and affected by, industry developments. Technology companies face intense competition and may be subject to extensive regulatory requirements.  They may have limited product lines, markets, financial resources, or personnel.  The products of technology companies may face obsolescence due to rapid technological developments, frequent new product introduction, and unpredictable changes in growth rates.
Foreign Securities Risk:  The Fund may invest in foreign companies.  There are specific risks associated with investing in foreign companies not typically associated with investing in domestic companies.  Risks include fluctuations in the exchange rates of foreign currencies, which may affect the U.S. dollar value of a security, and the possibility of substantial price volatility or reduced liquidity as a result of political and economic instability or policy and legislative changes in the foreign country.  Further, foreign companies may be subject to significantly higher levels of taxation than U.S. companies, including potentially confiscatory levels of taxation, thereby reducing the earnings potential of such foreign companies. Substantial withholding taxes may apply to distributions from foreign companies.
High Portfolio Turnover Risk:  High portfolio turnover will produce higher transaction costs (such as brokerage commissions and dealer markups) that the Fund must pay, thus reducing the Fund’s performance. High portfolio turnover may also result in higher taxes when Fund shares are held in a taxable account.
Risk Lose Money [Text] rr_RiskLoseMoney The value of your investment will fluctuate over time, and it is possible to lose money.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance Information
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock
The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the NASDAQ Composite Index and the S&P 500® Index.  For additional information on these indices, please see “Descriptions of Indices” on page 68 of this Prospectus.  The Fund is the successor to the FBR Technology Fund (the “Predecessor Technology Fund”).  The performance information provided for the periods on or prior to October 26, 2012, is historical information for the Predecessor Technology Fund, which had the same investment objective and substantially similar investment strategy as the Fund. The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.  Performance may be higher or lower in the future.  Updated performance information is available at www.hennessyfunds.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following performance information provides some indication of the risks of investing in the Fund by showing changes in its performance from year to year and how the Fund’s average annual returns for one, five, and ten years compare with those of indices that reflect broad measures of market performance, the NASDAQ Composite Index and the S&P 500® Index.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.hennessyfunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The Fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading HENNESSY TECHNOLOGY FUND CALENDAR YEAR TOTAL RETURNS OF INVESTOR SHARES
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
For the period shown in the bar chart, the Fund’s highest quarterly return was 21.05% for the quarter ended March 31, 2019, and the lowest quarterly return was -19.05% for the quarter ended September 30, 2011.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel highest quarterly return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Mar. 31, 2019
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.05%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel lowest quarterly return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (19.05%)
Performance Table Heading rr_PerformanceTableHeading AVERAGE ANNUAL TOTAL RETURNS (for the periods ended December 31, 2019)
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 The after-tax returns are calculated using the highest historical individual stated 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 individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock
Performance of the Fund’s Institutional Class shares differs from that of the Fund’s Investor Class shares because the share classes have different expenses and inception dates.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock
The after-tax returns are calculated using the highest historical individual stated federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an individual investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor Class shares only, and after-tax returns for Institutional Class shares will vary.
The inception date of the Fund’s Institutional Class shares is March 12, 2010.  Performance shown prior to the inception of Institutional Class shares reflects the performance of the Fund’s Investor Class shares and includes expenses that are not applicable to, and are higher than, those of Institutional Class shares.
Hennessy Technology Fund | NASDAQ Composite Index (reflects no deduction for fees, expenses, or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel NASDAQ Composite Index (reflects no deduction for fees, expenses, or taxes)
1 Year rr_AverageAnnualReturnYear01 36.69%
5 Years rr_AverageAnnualReturnYear05 14.93%
10 Years rr_AverageAnnualReturnYear10 16.10%
Hennessy Technology Fund | 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 31.49%
5 Years rr_AverageAnnualReturnYear05 11.70%
10 Years rr_AverageAnnualReturnYear10 13.56%
Hennessy Technology Fund | Investor Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HTECX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.15%
Component1 Other Expenses rr_Component1OtherExpensesOverAssets 0.10%
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 2.86% [12]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.96%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.85%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (2.61%) [13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 1.24%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 126
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 934
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,761
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,913
Annual Return 2010 rr_AnnualReturn2010 12.73%
Annual Return 2011 rr_AnnualReturn2011 (10.77%)
Annual Return 2012 rr_AnnualReturn2012 8.67%
Annual Return 2013 rr_AnnualReturn2013 29.75%
Annual Return 2014 rr_AnnualReturn2014 1.73%
Annual Return 2015 rr_AnnualReturn2015 3.46%
Annual Return 2016 rr_AnnualReturn2016 2.03%
Annual Return 2017 rr_AnnualReturn2017 20.20%
Annual Return 2018 rr_AnnualReturn2018 (1.82%)
Annual Return 2019 rr_AnnualReturn2019 39.10%
Label rr_AverageAnnualReturnLabel Hennessy Technology Fund – Investor Returns before taxes
1 Year rr_AverageAnnualReturnYear01 39.10%
5 Years rr_AverageAnnualReturnYear05 11.62%
10 Years rr_AverageAnnualReturnYear10 9.60%
Hennessy Technology Fund | Investor Class | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Technology Fund – Investor Return after taxes on distributions
1 Year rr_AverageAnnualReturnYear01 38.15%
5 Years rr_AverageAnnualReturnYear05 9.97%
10 Years rr_AverageAnnualReturnYear10 8.78%
Hennessy Technology Fund | Investor Class | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
Label rr_AverageAnnualReturnLabel Hennessy Technology Fund – Investor Return after taxes on distributions and sale of Fund shares
1 Year rr_AverageAnnualReturnYear01 23.67%
5 Years rr_AverageAnnualReturnYear05 8.69%
10 Years rr_AverageAnnualReturnYear10 7.61%
Hennessy Technology Fund | Institutional Class  
Prospectus [Line Items] rr_ProspectusLineItems  
Trading Symbol dei_TradingSymbol HTCIX
Shareholder Fee, Other rr_ShareholderFeeOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.74%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Component1 Other Expenses rr_Component1OtherExpensesOverAssets none
Component3 Other Expenses rr_Component3OtherExpensesOverAssets 2.74% [12]
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 2.74%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 3.48%
Fee Waiver or Reimbursement rr_FeeWaiverOrReimbursementOverAssets (2.49%) [13]
Net Expenses (as a percentage of Assets) rr_NetExpensesOverAssets 0.99%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 101
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 836
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,593
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,590
Label rr_AverageAnnualReturnLabel Hennessy Technology Fund – Institutional Returns before taxes
1 Year rr_AverageAnnualReturnYear01 39.48%
5 Years rr_AverageAnnualReturnYear05 11.97%
10 Years rr_AverageAnnualReturnYear10 9.89%
[1] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[2] Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[3] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[4] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[5] Prior to the reorganization that took place on October 26, 2018, Investor Class shares of the Fund were subject to a sales charge (load) on purchases. In connection with the reorganization, performance information has been restated to reflect the removal of the sales load.
[6] Includes state franchise taxes and federal and state income tax expenses, including deferred tax expenses (benefits). The Fund accrues a deferred tax liability (or asset) for its future tax liability associated with the Fund’s potential tax expense (benefit) if it were to recognize the unrealized gains (losses) in its portfolio. Such deferred tax expenses (benefits) may vary greatly from year to year and from day to day depending on the nature of the Fund’s investments, the performance of those investments, and general market conditions, and any estimate of deferred income tax expense (benefit) cannot be reliably predicted from year to year. While the Fund’s deferred income tax expense (benefit) for the prior fiscal year was zero, the Fund could accrue a deferred income tax expense (benefit) in the future that could significantly impact the Fund’s annual fund operating expenses and subsequently its net asset value.
[7] The Fund’s investment manager has contractually agreed to ensure that total operating expenses (exclusive of all federal, state, and local taxes, interest, brokerage commissions, dividend and interest expenses on short sales, acquired fund fees and expenses and other costs incurred in connection with the purchase and sale of securities, and extraordinary items) do not exceed 1.75% and 1.50% of the average daily net assets of the Investor Class and Institutional Class shares of the Fund, respectively. The contractual arrangement will continue until February 28, 2021, at which time the contractual arrangement will automatically terminate (and it may not be terminated prior to that date). The Fund’s investment manager may recoup reimbursed amounts for three years after the reimbursement occurred if total expenses, including such recoupment, do not exceed the annual expense limit in effect at the time of such reimbursement or such recoupment.
[8] Prior to the reorganization that took place on October 26, 2018, Investor Class shares of the Fund were subject to a sales charge (load) on purchases. In connection with the reorganization, performance information has been restated to reflect the removal of the sales load.
[9] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[10] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[11] Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[12] Includes acquired fund fees and expenses that do not exceed 0.01% of the Fund’s average daily net assets. Acquired fund fees and expenses are not reflected in the Fund’s financial statements, so the information presented in the expense table may differ from that presented in the financial highlights.
[13] The Fund’s investment manager has contractually agreed to ensure that total operating expenses (exclusive of all federal, state and local taxes, interest, brokerage commissions, 12b-1 fees, shareholder servicing fees payable to the Fund’s investment manager, acquired fund fees and expenses and other costs incurred in connection with the purchase and sale of securities, and extraordinary items) do not exceed 0.98% of the average daily net assets of Investor Class and Institutional Class shares of the Fund. The contractual arrangement will continue until February 28, 2021, at which time the contractual arrangement will automatically terminate (and it may not be terminated prior to that date). The Fund’s investment manager may recoup reimbursed amounts for three years after the reimbursement occurred if total expenses, including such recoupment, do not exceed the annual expense limit in effect at the time of such reimbursement or such recoupment.