Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Mar. 15, 2019
Jun. 29, 2018
Document And Entity Information      
Entity Registrant Name CM Seven Star Acquisition Corp    
Entity Central Index Key 0001713539    
Document Type 10-K    
Trading Symbol CMSS    
Document Period End Date Dec. 31, 2018    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity a Well-known Seasoned Issuer No    
Entity a Voluntary Filer No    
Entity's Reporting Status Current Yes    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
Entity Shell Company true    
Entity Small Business true    
Entity Filer Category Accelerated Filer    
Entity Public Float     $ 217,725,633
Entity Common Stock, Shares Outstanding   26,323,092  
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2018