Commitments and contingencies - Additional Information (Detail) - CNY (¥) ¥ in Thousands	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Capital commitment amount	¥ 0	¥ 0

The minimum amount the entity agreed to spend under the long-term purchase commitment.

No definition available.

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