Subsequent Event (Details)	12 Months Ended
	Sep. 30, 2012
Investor Class Shares [Member] | Hennessy Large Cap Financial Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Twelve B One Fee as Percent of Fund Assets	0.25%
Investor Class Shares [Member] | Hennessy Small Cap Financial Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Twelve B One Fee as Percent of Fund Assets	0.25%
Investor Class Shares [Member] | Hennessy Technology Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Twelve B One Fee as Percent of Fund Assets	0.25%
Investor Class Shares [Member] | Hennessy Focus Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Twelve B One Fee as Percent of Fund Assets	0.25%
Investor Class Shares [Member] | Hennessy Gas Utility Index Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.40%
Investor Class Shares [Member] | Hennessy Equity and Income Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.80%
Twelve B One Fee as Percent of Fund Assets	0.25%
Investor Class Shares [Member] | Hennessy Core Bond Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.80%
Twelve B One Fee as Percent of Fund Assets	0.25%
Institutional Class Shares [Member] | Hennessy Small Cap Financial Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Institutional Class Shares [Member] | Hennessy Technology Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Institutional Class Shares [Member] | Hennessy Focus Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.90%
Institutional Class Shares [Member] | Hennessy Equity and Income Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.80%
Institutional Class Shares [Member] | Hennessy Core Bond Fund [Member]
Fund [Abstract]
Management Fee as Percent of Fund Assets	0.80%