Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Product sales, net	$ 33,627	$ 26,678
Other revenue	941	0
Total revenue	34,568	26,678
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation of Revenue [Line Items]
Product sales, net	477	1,207
MACI Implants and Kits, and Epicel
Disaggregation of Revenue [Line Items]
Product sales, net	33,627	26,678
NexoBid revenue
Disaggregation of Revenue [Line Items]
Other revenue	900	0
Through Intermediary | Implants | Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net	13,206	11,338
Through Intermediary | Implants | Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net	4,280	3,730
Time-and-materials contract | Implants | Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net	849	436
Provider or Facility | Implants | Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net	4,466	3,109
Provider or Facility | NexoBid revenue
Disaggregation of Revenue [Line Items]
Other revenue	941	0
Directly to consumer | Biopsy kits
Disaggregation of Revenue [Line Items]
Product sales, net	519	466
Directly to consumer | Epicel
Disaggregation of Revenue [Line Items]
Product sales, net	$ 9,830	$ 6,392