Business combinations - Summary of Identified Assets Acquired and Liabilities Assumed (Detail) (Parenthetical)	Nov. 01, 2019	Aug. 31, 2018
Xingmu Group [Member]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquire, Percentage	14.50%	14.50%

Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination.

No definition available.

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant