Leases - supplemental cash flow information (Details) - CNY (¥) ¥ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Leases
Cash payments for operating leases	¥ 27,617	¥ 1,201
Right-of-use assets obtained in exchange for lease obligations	¥ 14,784	¥ 30,699

Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (g)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147478964/842-20-50-4

Name:	us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration