Other current assets - Additional Information (Detail) - USD ($)	3 Months Ended
Jan. 31, 2018	Oct. 31, 2017	Jan. 31, 2017
Increase (Decrease) In Other Noncurrent Assets	$ (21,000)		$ (20,000)
Notes Receivable [Member]
Increase (Decrease) In Other Noncurrent Assets	$ 0	$ 21,000

Amount of increase (decrease) in noncurrent assets classified as other.

No definition available.

Name:	us-gaap_IncreaseDecreaseInOtherNoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration