Income Taxes - Additional Information (Detail) - USD ($)	9 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Accruals of interest and penalties	$ 0		$ 0
Recognized interest or penalties	$ 0	$ 0

The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319

Name:	us-gaap_IncomeTaxExaminationPenaltiesAndInterestAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant