Related party transactions - Summary of Transactions Due From Related Parties (Parenthetical) (Detail) - Fei Wang [Member] - One Year Loan Agreement [Member] ¥ in Millions	Jan. 31, 2021 CNY (¥) shares
Schedule Of Transactions Due From Related Parties [Line Items]
Debt Instrument, Face Amount \| ¥	¥ 0.5
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Debt Instrument, Number of Stock Options Collateralized \| shares	515,000

Face (par) amount of debt instrument at time of issuance.

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