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Maximum aggregate fair market value of options granted to individual.

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Number of mutual funds.

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Number of open end mutual funds.

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Share based compensation arrangement by share based payment award exercise price percentage.

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Shareholder threshold percentage.

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Aggregate number of common shares reserved for future issuance.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Amount of realized and unrealized gain (loss) on investment.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of terms of share-based payment arrangement. Includes, but is not limited to, type of award or grantee and reason for issuance.

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The highest quantity of shares an employee can purchase under the plan per period.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Maximum number of shares that may be issued in accordance with the plan as a proportion of outstanding capital stock.

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Percentage of vesting of award under share-based payment arrangement.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Organization and Description of Business and Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2022 USD ($) Funds shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2017 shares	Aug. 31, 2022 shares	Aug. 31, 2010 shares
Number of Hennessy funds to which company provides investment advisory services \| Funds		16
Number of mutual funds \| Funds		30
Management contracts impairment amount \| $		$ 0	$ 0
Shares available for issuance		50.00%
Share based compensation percentage criteria description		more than 50% of the outstanding shares
Shares grant period					10 years
Maximum aggregate fair market value of shares \| $				$ 100,000
Maximum common stock issuable under plan		22,500,000	22,500,000
Maximum Vesting Period		4 years
Number of options available for grant				3,785,871
Minimum [Member]
Percentage of exercise price of fair value					110.00%
Maximum [Member]
Shares grant period					10 years
Maximum Vesting Period	5 years
Unrealized gains \| $		$ 1,000,000	$ 1,000,000
Buyback Program [Member]
Repurchase of common stock shares		0
Number of Shares Authorized to be repurchased						2,000,000	1,500,000
Number of shares remains available for repurchase under the program		1,096,368
Restricted Stock Units (RSUs) [Member]
Rate of restricted stock units vest under plan		25.00%
Incentive Stock Option Plan [Member] \| Minimum [Member]
Percentage of shareholder ownership to meet incentive stock option					10.00%
Stock Appreciation Right [Member] \| Maximum [Member]
Aggregate number of shares					75,000
Dividend Reinvestment And Stock Purchase Plan [Member]
Maximum common stock issuable under plan		1,470,000
Stock issued during period shares		7,612	12,666
Shares available for issuance under plan		1,452,845