Principal accounting policies (Schedule of Property and Equipment Estimated Useful Lives and Residual Rate) (Details)	12 Months Ended
Dec. 31, 2019
Buildings [Member]
Property and equipment [Line Items]
Estimated useful lives	40 years
Residual rate (as a percent)	0.00%
Servers, computers and equipment [Member] \| Minimum
Property and equipment [Line Items]
Estimated useful lives	3 years
Residual rate (as a percent)	0.00%
Servers, computers and equipment [Member] \| Maximum
Property and equipment [Line Items]
Estimated useful lives	5 years
Residual rate (as a percent)	5.00%
Leasehold improvements [Member]
Property and equipment [Line Items]
Residual rate (as a percent)	0.00%
Estimated useful lives	Shorter of lease term or 5 years
Decoration of buildings [Member]
Property and equipment [Line Items]
Estimated useful lives	10 years
Residual rate (as a percent)	0.00%
Motor vehicles [Member]
Property and equipment [Line Items]
Estimated useful lives	4 years
Motor vehicles [Member] \| Minimum
Property and equipment [Line Items]
Residual rate (as a percent)	0.00%
Motor vehicles [Member] \| Maximum
Property and equipment [Line Items]
Residual rate (as a percent)	5.00%
Furniture, fixture and office equipment [Member] \| Minimum
Property and equipment [Line Items]
Estimated useful lives	3 years
Residual rate (as a percent)	0.00%
Furniture, fixture and office equipment [Member] \| Maximum
Property and equipment [Line Items]
Estimated useful lives	5 years
Residual rate (as a percent)	5.00%

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=68071081&loc=d3e1205-110223

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Stated as a percentage, the estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose) divided by its [historical] capitalized cost.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_ComputerEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=yy_FurnitureFixturesAndOfficeEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: