v3.19.2
Document and Entity Information - shares
3 Months Ended
Mar. 30, 2019
May 31, 2019
Document and Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Entity Registrant Name TransMedics Group, Inc.  
Entity Central Index Key 0001756262  
Current Fiscal Year End Date --12-28  
Entity Current Reporting Status No  
Entity Filer Category Non-accelerated Filer  
Trading Symbol TMDX  
Entity Shell Company false  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Small Business true  
Entity Common Stock, Shares Outstanding   21,093,654