Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Tax Credit Carryforward [Line Items]
Gain on deconsolidation of Asterias	$ 0		$ 0	$ 49,048	$ 0
Unrealized gains recorded	40,015		0	26,532	0
Deferred income tax benefit	0		$ (948)	0	(3,395)
Deferred income tax benefit, federal					3,600
Deferred income tax expense (benefit), state taxes					$ 200
Asterias Biotherapeutics [Member]
Tax Credit Carryforward [Line Items]
Gain on deconsolidation of Asterias		$ 49,000		49,000
Unrealized gains recorded	$ 40,000			$ 26,500