Basis of Presentation, Liquidity and Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Liquidity [Abstract]
Accumulated deficit	$ 221,743		$ 221,743		$ 229,181
Shareholders' equity	$ 94,052		$ 94,052		$ 76,447
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average dilutive common shares used to compute diluted net income per common share (in shares)	95,801	78,362	95,360	78,312
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	57.10%		57.10%
Asterias Biotherapeutics [Member]
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	49.00%		49.00%
Parent [Member]
Liquidity [Abstract]
Accumulated deficit	$ (221,700)		$ (221,700)
Working capital	23,600		23,600
Shareholders' equity	94,100		94,100
Proceeds from equity financing after discount, commission and other expenses	18,900
Cash, cash equivalents and available for sale securities	$ 28,300		$ 28,300
Treasury Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average dilutive common shares used to compute diluted net income per common share (in shares)	2,400,000		3,400,000
Anti-dilutive shares excluded from computation of diluted loss per share (in shares)			0	4,894,000
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average dilutive common shares used to compute diluted net income per common share (in shares)	164,000		94,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average dilutive common shares used to compute diluted net income per common share (in shares)	164,000		94,000
Anti-dilutive shares excluded from computation of diluted loss per share (in shares)			5,679,000	4,212,000
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from computation of diluted loss per share (in shares)			9,395,000	9,191,000