Hennessy Cornerstone Growth Fund - Investor Class Energy Sector [Member] Financial Services Sector [Member] Healthcare Sector [Member] Real Estate [Member] Short-Term Investments and Other Sector [Member] 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 Collateralized Mortgage-Backed Securities [Member] U.S. Treasury Notes [Member] Hennessy Equity and Income Fund - Institutional Class Hennessy Balanced Fund - Investor Class Hennessy Energy Transition Fund - Investor Class Downstream Sector [Member] Exploration and Production Sector [Member] Integrated Sector [Member] Midstream Sector [Member] Oil Services Sector [Member] Hennessy Energy Transition Fund - Institutional Class Downstream [Member] Exploration and Production [Member] Integrated [Member] Midstream [Member] Oil Services [Member] Short-Term Investments and Other [Member] Hennessy Midstream Fund - Investor Class Crude Oil and Refined Products [Member] Geathering and Processing [Member] Natural Gas/NGL Transportation [Member] Hennessy Midstream Fund - Institutional Class Hennessy Gas Utility Fund - Investor Class Hennessy Gas Utility Fund - Institutional Class Hennessy Japan Fund - Investor Class Real Estate Sector [Member] 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 Hennessy Technology Fund - Investor Class Hennessy Technology Fund - Institutional Class Hennessy Sustainable ETF Hennessy Cornerstone Growth Fund - Investor Class Short-Term Investments and Other Sector. 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. U.S. Treasury Notes. Hennessy Equity and Income Fund - Institutional Class. Hennessy Balanced Fund - Investor Class Hennessy Energy Transition Fund - Investor Class Downstream Sector. Exploration and Production Sector. Integrated Sector. Oil Services Sector. Midstream Sector. Hennessy Energy Transition Fund - Institutional Class. Downstream. Exploration and Production. Integrated. Midstream. Oil Services. Short-Term Investments and Other. Hennessy Midstream Fund - Investor Class Crude Oil and Refined Products. Geathering and Processing. Natural Gas/NGL Transportation. Hennessy Midstream Fund - Institutional 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. Hennessy Technology Fund - Investor Class. Hennessy Technology Fund - Institutional Class. Hennessy Sustainable ETF. Net Assets Investment Company, Portfolio Turnover