Nature of Business - Reverse Stock Split (Details) - Histogenics	9 Months Ended
Sep. 30, 2020
Nature of Business
Shares issued exchange rate to former Ocugen's stockholders (in USD per share)	0.4794
Stock split, conversion ratio	0.0167

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187143-122770

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