v3.19.3
Document and Entity Information - shares
9 Months Ended
Sep. 28, 2019
Oct. 31, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 28, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Registrant Name TransMedics Group, Inc.  
Entity Central Index Key 0001756262  
Current Fiscal Year End Date --12-28  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
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   21,163,664
Entity File Number 001-38891  
Entity Incorporation, State or Country Code MA  
Entity Tax Identification Number 83-2181531  
Entity Address, Address Line One 200 Minuteman Road  
Entity Address, City or Town Andover  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 01810  
City Area Code (978)  
Local Phone Number 552-0900  
Document Quarterly Report true  
Document Transition Report false  
Title of 12(b) Security Common Stock, No Par Value  
Security Exchange Name NASDAQ