Fair value portion of assets classified as held for sale.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

Name:	us-gaap_AssetsHeldForSaleLongLivedFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Merger and Pre-Merger Financing - NeoCart (Details) - USD ($) $ in Millions	Oct. 31, 2019	May 08, 2019	Dec. 31, 2020
Histogenics
Merger and Financing
Asset purchase agreement, cash consideration	$ 7.0	$ 6.5
Percentage of purchase price increase per month	10.00%
Neocart \| Level 2
Merger and Financing
Quoted price of assets held for sale of NeoCart			$ 7.0