Hennessy Cornerstone Growth Fund Formula Investing Risk [Member] Growth and Value Investing Risk [Member] Small-Sized and Medium-Sized Companies Risk [Member] Industry Concentration Risk [Member] High Portfolio Turnover Risk [Member] Foreign Securities Risk [Member] Market and Equity Investments Risk [Member] Tax Law Change Risk [Member] Hennessy Focus Fund Real Estate Investment Risk [Member] Temporary Defensive Positions Risk [Member] Hennessy Cornerstone Mid Cap 30 Fund Hennessy Cornerstone Large Growth Fund Medium-Sized Company Risk [Member] Hennessy Cornerstone Value Fund Value Investing Risk [Member] Medium-Sized Companies Risk [Member] Hennessy Total Return Fund Borrowing Risk [Member] Hennessy Equity and Income Fund Debt Investments Risk [Member] Asset-Backed and Mortgage-Backed Securities Risk [Member] Investment Company Securities Risk [Member] ETF Risk [Member] Hennessy Balanced Fund Hennessy Energy Transition Fund Hennessy Energy Transition Fund - Investor Class Hennessy Energy Transition Fund - Institutional Class MLP Risk [Member] MLP Tax Risk [Member] Cash Flow Risk [Member] RIC Qualification Risk [Member] Liquidity Risk [Member] Hennessy Midstream Fund Hennessy Midstream Fund - Investor Class Hennessy Midstream Fund - Institutional Class Tax Risks [Member] Fund Structure Risk [Member] Tax Estimation/NAV Risk [Member] Dividend Distribution Risk [Member] Hennessy Gas Utility Fund Index Tracking Risk [Member] Hennessy Japan Fund Foreign Securities, Foreign Currency, and Japan-Specific Risk [Member] Hennessy Japan Small Cap Fund Hennessy Large Cap Financial Fund Mortgage and Real Estate Investments Risk [Member] Hennessy Small Cap Financial Fund Hennessy Technology Fund Hennessy Technology Fund - Investor Class Hennessy Technology Fund - Institutional Class Hennessy Sustainable ETF Hennessy Sustainable ETF [Member] Structural ETF Risks [Member] Cash Transactions Risk [Member] Market Participants Risk [Member] Costs of Buying and Selling Fund Shares [Member] Premium/Discount Risk [Member] Trading Risks [Member] Early Close/Trading Halt Risk [Member] Sustainability Investing Risk [Member] Third-Party Data Provider Risk [Member] Large-Sized Companies Risk [Member] Model Risk [Member] Hennessy Cornerstone Growth Fund - Investor Class Hennessy Cornerstone Growth Fund - Institutional Class Hennessy Focus Fund - Investor Class Hennessy Focus Fund - Institutional Class Hennessy Cornerstone Mid Cap 30 Fund - Investor Class Hennessy Cornerstone Mid Cap 30 Fund - Institutional Class Hennessy Cornerstone Large Growth Fund - Investor Class Hennessy Cornerstone Large Growth Fund - Institutional Class Hennessy Cornerstone Value Fund - Investor Class Hennessy Cornerstone Value Fund - Institutional Class Hennessy Total Return Fund - Investor Class Hennessy Equity and Income Fund - Investor Class Hennessy Equity and Income Fund - Institutional Class Hennessy Balanced Fund - Investor Class Hennessy Gas Utility Fund - Investor Class Hennessy Gas Utility Fund - Institutional Class Hennessy Japan Fund - Investor Class Hennessy Japan Fund - Institutional Class Hennessy Japan Small Cap Fund - Investor Class Hennessy Japan Small Cap Fund - Institutional Class Hennessy Large Cap Financial Fund - Investor Class Hennessy Large Cap Financial Fund - Institutional Class Hennessy Small Cap Financial Fund - Investor Class Hennessy Small Cap Financial Fund - Institutional Class Russell 3000® Index (reflects no deduction for fees, expenses, or taxes) Russell Midcap® Growth Index (reflects no deduction for fees, expenses, or taxes) Russell 2000® Index (reflects no deduction for fees, expenses, or taxes) S&P 500® Index (reflects no deduction for fees, expenses, or taxes) Russell Midcap® Index (reflects no deduction for fees, expenses, or taxes) Russell 1000® Index (reflects no deduction for fees, expenses, or taxes) Russell 1000® Value Index (reflects no deduction for fees, expenses, or taxes) 75/25 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes) Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes) 50/50 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes) S&P 500® Energy Index (reflects no deduction for fees, expenses, or taxes) Alerian US Midstream Energy Index (reflects no deduction for fees, expenses, or taxes) AGA Stock Index (reflects no deduction forfees, expenses, or taxes) Russell/Nomura Total Market Index (reflects no deduction for fees, expenses, or taxes) TOPIX (reflects no deduction for fees, expenses, or taxes) Russell/Nomura Small Cap Index (reflects no deduction for fees, expenses, or taxes) Russell 1000® Index Financials (reflects no deduction for fees, expenses, or taxes) Russell 2000® Index Financials (reflects no deduction for fees, expenses, or taxes) Nasdaq Composite Index (reflects no deduction for fees, expenses, or taxes) S&P 500® Equal Weight Index (reflects no deduction for fees, expenses, or taxes) Hennessy Cornerstone Growth Fund. Hennessy Cornerstone Growth Fund - Investor Class. Hennessy Cornerstone Growth Fund - Institutional Class. Hennessy Focus Fund. Hennessy Focus Fund - Investor Class. Hennessy Focus Fund - Institutional Class. Hennessy Cornerstone Mid Cap 30 Fund. Hennessy Cornerstone Mid Cap 30 Fund - Investor Class. Hennessy Cornerstone Mid Cap 30 Fund - Institutional Class. Hennessy Cornerstone Large Growth Fund. Hennessy Cornerstone Large Growth Fund - Investor Class. Hennessy Cornerstone Large Growth Fund - Institutional Class. Hennessy Cornerstone Value Fund. Hennessy Cornerstone Value Fund - Investor Class. Hennessy Cornerstone Value Fund - Institutional Class. Hennessy Total Return Fund. Hennessy Total Return Fund - Investor Class. Hennessy Equity and Income Fund. Hennessy Equity and Income Fund - Institutional Class. Hennessy Equity and Income Fund - Investor Class. Hennessy Balanced Fund. Hennessy Balanced Fund - Investor Class. Hennessy Energy Transition Fund. Hennessy Energy Transition Fund - Institutional Class. Hennessy Energy Transition Fund - Investor Class. Hennessy Midstream Fund. Hennessy Midstream Fund - Investor Class. Hennessy Midstream Fund - Institutional Class. Hennessy Gas Utility Fund. Hennessy Gas Utility Fund - Investor Class. Hennessy Gas Utility Fund - Institutional Class. Hennessy Japan Fund. Hennessy Japan Fund - Institutional Class. Hennessy Japan Fund - Investor Class. Hennessy Japan Small Cap Fund. Hennessy Japan Small Cap Fund - Investor Class. Hennessy Japan Small Cap Fund - Institutional Class. Hennessy Large Cap Financial Fund. Hennessy Large Cap Financial Fund - Investor Class. Hennessy Large Cap Financial Fund - Institutional Class. Hennessy Small Cap Financial Fund. Hennessy Small Cap Financial Fund - Investor Class. Hennessy Small Cap Financial Fund - Institutional Class. Hennessy Technology Fund. Hennessy Technology Fund - Investor Class. Hennessy Technology Fund - Institutional Class. Hennessy Sustainable ETF. Hennessy Sustainable ETF. Tax Law Change Risk. High Portfolio Turnover Risk. Model Risk. Small-Sized and Medium-Sized Companies Risk. Large-Sized Companies Risk. Market and Equity Investments Risk. Third-Party Data Provider Risk. Sustainability Investing Risk. Early Close/Trading Halt Risk. Trading Risks. Premium/Discount Risk. Costs of Buying and Selling Fund Shares. Market Participants Risk. Cash Transactions Risk. Structural ETF Risks. Foreign Securities Risk. Industry Concentration Risk. Temporary Defensive Positions Risk. Mortgage and Real Estate Investments Risk. Medium-Sized Companies Risk. ETF Risk. Investment Company Securities Risk. Foreign Securities, Foreign Currency, and Japan-Specific Risk. Index Tracking Risk. Liquidity Risk. Medium-Sized Company Risk. Cash Flow Risk. Dividend Distribution Risk. MLP Risk. Tax Estimation/NAV Risk. MLP Tax Risk. Fund Structure Risk. Tax Risks. RIC Qualification Risk. Formula Investing Risk. Asset-Backed and Mortgage-Backed Securities Risk. Debt Investments Risk. Borrowing Risk. Value Investing Risk. Growth and Value Investing Risk. Real Estate Investment Risk. Russell 2000® Index (reflects no deduction for fees, expenses, or taxes). S&P 500® Index (reflects no deduction for fees, expenses, or taxes). Russell 3000® Index (reflects no deduction for fees, expenses, or taxes). Russell Midcap® Growth Index (reflects no deduction for fees, expenses, or taxes). Russell Midcap® Index (reflects no deduction for fees, expenses, or taxes). Russell 1000® Index (reflects no deduction for fees, expenses, or taxes) Russell 1000® Value Index (reflects no deduction for fees, expenses, or taxes). Dow Jones Industrial Average (reflects no deduction for fees, expenses, or taxes). S&P 500® Equal Weight Index (reflects no deduction for fees, expenses, or taxes). Nasdaq Composite Index (reflects no deduction for fees, expenses, or taxes). AGA Stock Index (reflects no deduction forfees, expenses, or taxes). Russell 2000® Index Financials (reflects no deduction for fees, expenses, or taxes). Russell 1000® Index Financials (reflects no deduction for fees, expenses, or taxes). Russell/Nomura Total Market Index (reflects no deduction for fees, expenses, or taxes). TOPIX (reflects no deduction for fees, expenses, or taxes). Russell/Nomura Small Cap Index (reflects no deduction for fees, expenses, or taxes). 50/50 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes) Alerian US Midstream Energy Index (reflects no deduction for fees, expenses, or taxes). 75/25 Blended DJIA/Treasury Index (reflects no deduction for fees, expenses, or taxes) S&P 500® Energy Index (reflects no deduction for fees, expenses, or taxes)