Asterias Merger - Schedule of Valuation of Identifiable Intangible Assets and Their Estimated Useful Lives (Details) - Asterias Biotherapeutics, Inc. [Member] $ in Thousands	6 Months Ended
Jun. 30, 2019 USD ($)
Preliminary Estimated Asset Fair Value	$ 47,190
In Process Research and Development [Member]
Preliminary Estimated Asset Fair Value	$ 46,540
Useful Life (Years)	0 years
Royalty Contracts [Member]
Preliminary Estimated Asset Fair Value	$ 650
Useful Life (Years)	5 years

Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=116869197&loc=d3e4845-128472

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