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Asterias Merger (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended
	Mar. 08, 2019	Mar. 08, 2019	Sep. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	May 08, 2019	Dec. 31, 2018	May 13, 2016
Closing price of common stock				$ 162,844			$ 93,840
Number of warrants issued to purchase of common stock								2,813,159
Fair value of warrants				$ (37)	$ 108
Common stock held in investment	2,621,811	2,621,811
Share price, per share	$ 1.31	$ 1.31					$ 0.62
Fair value of Equity method investment, shares				21,700
Fair value of Equity method investment, value	$ 20,200	$ 20,200					$ 13,500
General and Administrative [Member]
Acquisition related costs				$ 3,500
April, 2019 [Member]
Number of warrants issued to purchase of common stock				907,442
Fair value of warrants				$ 372
Common Stock [Member]
Number of warrants issued to purchase of common stock								2,959,559
Exercise price								$ 4.37
Warrant term								5 years
Warrant expiration date								May 13, 2021
BioTime Warrants [Member]
Exercise price				$ 6.15
Warrant expiration date				May 31, 2021
Fair value of warrants				$ 495
AST Clinical Program [Member]
Identifiable intangible asset acquired		46,500
Royalty Contracts [Member]
Useful life of asset				5 years
In Process Research and Development [Member]
Identifiable intangible asset acquired		31,700
Regenerative Medicine [Member]
Identifiable intangible asset acquired		$ 14,800
30 Days After the Closing of Asterian Merger [Member] \| BioTime Warrants [Member]
Number of warrants issued to purchase of common stock				1,089,900
December 31, 2018 to March 8, 2019 [Member]
Unrealized loss				$ 6,700
December 31, 2017 to March 31, 2018 [Member]
Unrealized loss					$ 17,400
December 31, 2017 to March 31, 2018 [Member] \| Maximum [Member]
Share price, per share					$ 2.25
December 31, 2017 to March 31, 2018 [Member] \| Minimum [Member]
Share price, per share					$ 1.45
Parent Company [Member]
Number of warrants issued to purchase of common stock				1,997,340
Parent Company [Member] \| April, 2019 [Member]
Fair value of warrants				$ 332
Exchange of shares				251,835
Exchange for cash				$ 40
Asterias [Member]
Upfront payment received			$ 1,000
Estimated purchase price			$ 200
Ownership interest				38.00%
Merger Consideration [Member] \| Parent Company [Member]
Stock-for-stock transaction	24,695,898	24,695,898
Closing price of common stock						$ 32,400
Merger Consideration [Member] \| Asterias [Member]
Stock-for-stock transaction	0.71	0.71
Merger Consideration [Member] \| Asterias [Member] \| Restricted Stock [Member]
Stock-for-stock transaction	58,085	58,085