Investment Advisory and Shareholder Service Fee Revenue (Details) (USD $)	9 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	0.74%
Rate at which shareholders service fees charged	0.10%
Amount by which net profits exceed the positive balance	20% of the amount by which net profits exceed the positive balance
Initial balance of memorandum account	$ 0
Incentive fees earned
Hennessy Select Large Value Fund [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	0.85%
Hennessy Select Large Value Fund [Member] | RBC Global Asset Management (U.S.) Inc [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Portfolio management fees paid, annual rate of average daily net assets, Percentage	0.35%
Hennessy Select SPARX Japan Fund [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	1.00%
Hennessy Select SPARX Japan Fund [Member] | RBC Global Asset Management (U.S.) Inc [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Portfolio management fees paid, annual rate of average daily net assets, Percentage	0.35%
Hennessy Select SPARX Japan Smaller Companies Fund [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	1.20%
Hennessy Select SPARX Japan Smaller Companies Fund [Member] | RBC Global Asset Management (U.S.) Inc [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Portfolio management fees paid, annual rate of average daily net assets, Percentage	0.20%
Hennessy Balanced Fund and Hennessy Total Return Fund [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	0.60%
Micro Cap Fund [Member]
Investment Advisory and Shareholder Service Fee Revenue (Textual) [Abstract]
Investment advisory fees received, annual rate of average daily net assets, Percentage	2.00%