Income tax benefit - Additional Information (Detail) - USD ($)	3 Months Ended
Jan. 31, 2017	Jan. 31, 2016	Oct. 31, 2016
Income Taxes [Line Items]
Provision for income tax as percentage of income (loss) before income taxes	30.00%	45.00%
Unrecognized tax benefits	$ 0		$ 0
Accrued interest and penalties related to uncertain tax positions	$ 0		$ 0

Amount of unrecognized tax benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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