Income taxes - Summary of Valuation Allowance (Detail) - CNY (¥) ¥ in Thousands	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Beginning balance	¥ 149,978	¥ 112,539
Change of valuation allowance	27,269	37,439
Ending balance	¥ 177,247	¥ 149,978

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319

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