Financial Statements Schedule I - Additional Information (Details)	Dec. 31, 2018
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]
Percentage of restricted net assets of subsidiary exceeding consolidated net assets	25.00%

Percentage of restricted net assets of subsidiary exceeding consolidated net assets.

No definition available.

Name:	zlab_PercentageOfRestrictedNetAssetsOfSubsidiaryExceedingConsolidatedNetAssets
Namespace Prefix:	zlab_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant