Investment Advisory Agreements	9 Months Ended
Jun. 30, 2018
Text Block [Abstract]
Investment Advisory Agreements	(3) Investment Advisory Agreements The Company has management contracts with Hennessy Funds Trust, under which it provides investment advisory services to all classes of the 14 Hennessy Funds. The management contracts must be renewed annually (except in limited circumstances) by (i) the Funds’ Board of Trustees or the vote of a majority of the outstanding shares of the applicable Hennessy Fund and (ii) the vote of a majority of the trustees of Hennessy Funds Trust who are not interested persons of the Hennessy Funds. If the management contracts are not renewed annually as described above, they will terminate automatically. There are two additional circumstances in which the management contracts would terminate. First, the management contracts would automatically terminate if the Company assigned them to another advisor (assignment includes “indirect assignment,” which is the transfer of the Company’s common stock in sufficient quantities deemed to constitute a controlling block). Second, each management contract may be terminated prior to its expiration upon 60 days’ notice by either the Company or the applicable Hennessy Fund. As provided in the management contracts with the 14 Hennessy Funds, the Company receives investment advisory fees monthly based on a percentage of the respective fund’s average daily net assets. The Company has entered into sub-advisory agreements for the Hennessy Focus Fund, the Hennessy Equity and Income Fund, the Hennessy Japan Fund, and the Hennessy Japan Small Cap Fund. Under each of these sub-advisory agreements, the sub-advisor is responsible for the investment of the assets of the applicable Hennessy Fund in accordance with the terms of such agreement and the applicable Hennessy Fund’s Prospectus and Statement of Additional Information. The sub-advisors are subject to the direction, supervision, and control of the Company and the Funds’ Board of Trustees. The sub-advisory agreements must be renewed annually (except in limited circumstances) in the same manner as, and are subject to the same termination provisions as, the management contracts. In exchange for the sub-advisory services, the Company (not the Hennessy Funds) pays sub-advisory fees to the sub-advisors out of its own assets. Sub-advisory fees are calculated as a percentage of the applicable sub-advised fund’s average daily net asset value.

(3) Investment Advisory Agreements

The Company has management contracts with Hennessy Funds Trust, under which it provides investment advisory services to all classes of the 14 Hennessy Funds.

The management contracts must be renewed annually (except in limited circumstances) by (i) the Funds’ Board of Trustees or the vote of a majority of the outstanding shares of the applicable Hennessy Fund and (ii) the vote of a majority of the trustees of Hennessy Funds Trust who are not interested persons of the Hennessy Funds. If the management contracts are not renewed annually as described above, they will terminate automatically. There are two additional circumstances in which the management contracts would terminate. First, the management contracts would automatically terminate if the Company assigned them to another advisor (assignment includes “indirect assignment,” which is the transfer of the Company’s common stock in sufficient quantities deemed to constitute a controlling block). Second, each management contract may be terminated prior to its expiration upon 60 days’ notice by either the Company or the applicable Hennessy Fund.

As provided in the management contracts with the 14 Hennessy Funds, the Company receives investment advisory fees monthly based on a percentage of the respective fund’s average daily net assets.

The Company has entered into sub-advisory agreements for the Hennessy Focus Fund, the Hennessy Equity and Income Fund, the Hennessy Japan Fund, and the Hennessy Japan Small Cap Fund. Under each of these sub-advisory agreements, the sub-advisor is responsible for the investment of the assets of the applicable Hennessy Fund in accordance with the terms of such agreement and the applicable Hennessy Fund’s Prospectus and Statement of Additional Information. The sub-advisors are subject to the direction, supervision, and control of the Company and the Funds’ Board of Trustees. The sub-advisory agreements must be renewed annually (except in limited circumstances) in the same manner as, and are subject to the same termination provisions as, the management contracts.

In exchange for the sub-advisory services, the Company (not the Hennessy Funds) pays sub-advisory fees to the sub-advisors out of its own assets. Sub-advisory fees are calculated as a percentage of the applicable sub-advised fund’s average daily net asset value.