Principal Accounting Policies - Property and equipment, net (Details)	12 Months Ended
Dec. 31, 2021
Computers
Property and Equipment
Estimated Useful Lives	3 years
Equipment, furniture and motor vehicles
Property and Equipment
Estimated Useful Lives	5 years
Leasehold improvements
Property and Equipment
Estimated Useful Lives	Lesser of lease terms or the estimated useful lives of the assets

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 35
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123364984&loc=d3e1205-110223

Name:	us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration