Deconsolidation of Asterias (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
	May 13, 2016	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Noncontrolling Interest [Line Items]
Common stock, outstanding (in shares)		102,772,000			102,772,000		90,421,000
Gain on deconsolidation		$ 0		$ 0	$ 49,048	$ 0
Asterias Biotherapeutics, Inc. [Member]
Noncontrolling Interest [Line Items]
Number of shares sold (in shares)	5,147,059
Warrants issued to purchase common stock (in shares)	2,959,559
Proceeds from sale of stock	$ 16,200
Number of units available through offerings (in shares)	708,333
Percentage of ownership interest outstanding after offering	48.70%				47.00%
Common stock, outstanding (in shares)	3,852,880	21,700,000			21,700,000
Gain on deconsolidation			$ 49,000		$ 49,000