XML 31 R20.htm IDEA: XBRL DOCUMENT v3.4.0.3

Basis of Financial Statement Presentation - Additional Information (Detail)	6 Months Ended
	Mar. 31, 2016 Funds
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of Hennessy funds to which company provides investment advisory services	16
Contractual expense ratio limitations termination date	Feb. 28, 2015

X

- Definition

Contractual agreement termination date.

+ References

No definition available.

+ Details

Name:	hnna_ContractualAgreementTerminationDate
Namespace Prefix:	hnna_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of open end mutual funds.

+ References

No definition available.

+ Details

Name:	hnna_NumberOfOpenEndMutualFunds
Namespace Prefix:	hnna_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration