Stockholders' Equity - Schedule of Reconciliation of Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 02, 2019	Mar. 31, 2019	Mar. 31, 2018
Beginning balance	$ 92,246	$ 92,246	$ 164,263
Cumulative-effect adjustment for adoption of Accounting Standard Codification	100
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes		(75)	(7)
Stock-based compensation		1,361	809
Stock-based compensation in subsidiaries			175
Sale of subsidiary warrants in AgeX			737
Subsidiary financing transactions with noncontrolling interests - AgeX
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services		79
Foreign currency translation adjustments		(732)	75
Shares issued in connection with the Asterias Merger		32,353
Shares retired in connection with the Asterias Merger		(3,435)
Tax effect of accumulated other comprehensive income		(732)
NET INCOME/(LOSS)		39,296	(63,698)
Ending balance		161,236	102,455
ASU 2014-09 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification			101
ASU 2016-02 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification		143
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Preferred Shares [Member]
Beginning balance
Beginning balance, shares
Cumulative-effect adjustment for adoption of Accounting Standard Codification
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes
Stock-based compensation
Stock-based compensation, shares
Stock-based compensation in subsidiaries
Sale of subsidiary warrants in AgeX
Subsidiary financing transactions with noncontrolling interests - AgeX
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services, shares
Foreign currency translation adjustments
Shares issued in connection with the Asterias Merger
Shares issued in connection with the Asterias Merger, shares
Shares retired in connection with the Asterias Merger
Tax effect of accumulated other comprehensive income
Ending balance
Ending balance, shares
Common Shares [Member]
Beginning balance	$ 354,270	$ 354,270	$ 378,487
Beginning balance, shares	127,136,000	127,136,000	126,866,000
Cumulative-effect adjustment for adoption of Accounting Standard Codification
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes		$ (75)	$ (7)
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes, shares		118,000	3,000
Stock-based compensation		$ 1,361	$ 809
Stock-based compensation, shares
Stock-based compensation in subsidiaries
Sale of subsidiary warrants in AgeX
Subsidiary financing transactions with noncontrolling interests - AgeX			$ (103)
Subsidiary financing transactions with noncontrolling interests - AgeX, shares
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services		$ 79
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services, shares		60,000
Foreign currency translation adjustments
Shares issued in connection with the Asterias Merger		$ 32,353
Shares issued in connection with the Asterias Merger, shares		24,696,000
Shares retired in connection with the Asterias Merger		$ (3,435)
Shares retired in connection with the Asterias Merger, shares		(2,622,000)
Tax effect of accumulated other comprehensive income
NET INCOME/(LOSS)
Ending balance		$ 384,553	$ 379,186
Ending balance, shares		149,388,000	126,869,000
Accumulated Deficit [Member]
Beginning balance	$ (261,856)	$ (261,856)	$ (216,297)
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes
Stock-based compensation
Stock-based compensation in subsidiaries
Sale of subsidiary warrants in AgeX
Subsidiary financing transactions with noncontrolling interests - AgeX
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Foreign currency translation adjustments
Shares issued in connection with the Asterias Merger
Shares retired in connection with the Asterias Merger
Tax effect of accumulated other comprehensive income
NET INCOME/(LOSS)		39,310	(63,548)
Ending balance		(222,403)	(279,416)
Accumulated Deficit [Member] | ASU 2016-01 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification			328
Accumulated Deficit [Member] | ASU 2014-09 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification			101
Accumulated Deficit [Member] | ASU 2016-02 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification		143
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Noncontrolling Interest/(Deficit) [Member]
Beginning balance	(1,594)	(1,594)	1,622
Cumulative-effect adjustment for adoption of Accounting Standard Codification
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes
Stock-based compensation
Stock-based compensation in subsidiaries			175
Sale of subsidiary warrants in AgeX			737
Subsidiary financing transactions with noncontrolling interests - AgeX			103
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Foreign currency translation adjustments
Shares issued in connection with the Asterias Merger
Shares retired in connection with the Asterias Merger
Tax effect of accumulated other comprehensive income
NET INCOME/(LOSS)		(14)	(150)
Ending balance		(1,608)	2,487
Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning balance	$ 1,426	1,426	451
Cumulative-effect adjustment for adoption of Accounting Standard Codification
Shares issued upon vesting of restricted stock units, net of shares retired to pay employees' taxes
Stock-based compensation
Stock-based compensation in subsidiaries
Sale of subsidiary warrants in AgeX
Subsidiary financing transactions with noncontrolling interests - AgeX
Stock-based compensation for shares issued upon vesting of Asterias restricted stock units attributable to post combination services
Foreign currency translation adjustments			75
Shares issued in connection with the Asterias Merger
Shares retired in connection with the Asterias Merger
Tax effect of accumulated other comprehensive income		(732)
NET INCOME/(LOSS)
Ending balance		$ 694	198
Accumulated Other Comprehensive Income/(Loss) [Member] | ASU 2016-01 [Member]
Cumulative-effect adjustment for adoption of Accounting Standard Codification			$ (328)