Unaudited interim condensed consolidated financial statements - Estimated Impact on adoption of ASU 2016-02: Leases (Detail) - USD ($) $ in Thousands	Nov. 01, 2019	Jan. 31, 2020	Oct. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Lease, Practical Expedients, Package	true
Lease, Practical Expedient, Lessor Single Lease Component	true
Lessor, Combined Component, Topic	Topic 842
Operating lease ROU asset		$ 2,024	$ 0
Lease liabilities		$ 2,124
Accounting Standards Update No. 2016-02: Leases | Forecast Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU asset	$ 2,300
Lease liabilities	$ 2,400