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Principal accounting policies (Schedule of Amortization of Finite-lived Intangible Assets is Computed Using Straight-line Method Over Following Estimated Useful Lives) (Details)	12 Months Ended
	Dec. 31, 2018
Operating rights [Member]
Intangible assets, net [Line Items]
Estimated useful lives	Shorter of the economic life or contract terms
Software [Member] | Minimum [Member]
Intangible assets, net [Line Items]
Estimated useful lives	3 years
Software [Member] | Maximum [Member]
Intangible assets, net [Line Items]
Estimated useful lives	5 years
Domain names [Member]
Intangible assets, net [Line Items]
Estimated useful lives	15 years
Technology [Member]
Intangible assets, net [Line Items]
Estimated useful lives	5 years
License [Member]
Intangible assets, net [Line Items]
Estimated useful lives	15 years

X

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

X

- 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

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

X

- Definition

Describes the periods of time over which an entity anticipates to receive from finite-lived intangible asset estimated useful lives.

+ References

No definition available.

+ Details

Name:	yy_FiniteLivedIntangibleAssetUsefulLives
Namespace Prefix:	yy_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_InternetDomainNamesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PatentedTechnologyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_LicenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: