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CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) pure in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Conversion ratio, ADS to Class A ordinary share | 10 | 10 | 10

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- Definition Conversion ratio of American Depositary Share (ADS) to Class A ordinary share. + References No definition available. + Details
Name: | cmcm_SharesConversionRatio
Namespace Prefix: | cmcm_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration