Supplemental Cash Flow Information - Schedule of Condensed Consolidated Statements of Cash Flows (Details) - Asterias Biotherapeutics, Inc. [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Issuance of common stock for the Asterias Merger	$ 32,353
Assumption of liabilities in the Asterias Merger	1,136
Assumptions of warrants in the Asterias Merger	$ 867

The fair value of stock issued in noncash financing activities.

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