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Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Commitments and Contingencies - Service Agreements (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tissue Processing Agreement [Member]
Service Agreements
License fee amount		$ 2,148	$ 1,931	$ 1,409
Master Services Agreement For Clinical Research and Related Services [Member]
Service Agreements
Service agreement amount paid upon execution of agreement	$ 151