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Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended				3 Months Ended		12 Months Ended
	Nov. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Nov. 30, 2015	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Related party payables					$ 2,173,000		$ 256,000
Shares issued as payment for services					831,000	$ 2,941,000
Noncash dividend income					12,000	4,883,000
Fair value of financial assets measured at fair value on a recurring basis					77,283,000		122,181,000
Revenues					23,335,000	39,666,000
Third Security, LLC
Related Party Transaction [Line Items]
Initial term of services agreement				1 year
Expense for services					17,000	14,000
Shares issued as payment for services						$ 2,041,000
Shares issued as payment for services (in shares)						160,626
Sublease rental income					22,000	$ 21,000
Third Security, LLC \| Common Stock
Related Party Transaction [Line Items]
Expense for services				$ 800,000
Related party payables					2,078,000
Convertible Note and Warrants \| Other Noncurrent Assets \| Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Fair value of financial assets measured at fair value on a recurring basis					$ 156,000		120,000
Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Convertible preferred shares issued (in shares)		1,161
Warrants, number of common shares into which warrants can be converted (in shares)		99,769
Convertible preferred shares, dividend rate		4.00%
ZIOPHARM Oncology, Inc.
Related Party Transaction [Line Items]
Preferred shares, stated value (in usd per share)			$ 1,200
Preferred shares, dividend rate (in usd per share)			$ 12.00
Third Security, LLC \| Chief Executive Officer
Related Party Transaction [Line Items]
Ownership interest					100.00%
Collaboration and licensing agreements
Related Party Transaction [Line Items]
Revenues					$ 5,970,000	19,848,000
Collaboration and licensing agreements \| Histogenics Corporation, OvaScience Inc., and Synthetic Biologics Inc.
Related Party Transaction [Line Items]
Revenues						$ 3,183,000	11,877,000
ZIOPHARM Oncology, Inc.
Related Party Transaction [Line Items]
Dividend income, number of preferred shares received (in shares)						3,624
Noncash dividend income						$ 4,871,000
Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Purchases of preferred stock and warrants		$ 1,161,000
Preferred stock \| Fibrocell Science, Inc. \| Other Noncurrent Assets
Related Party Transaction [Line Items]
Fair value of financial assets measured at fair value on a recurring basis					248,000		191,000
Preferred stock \| Oragenics, Inc.
Related Party Transaction [Line Items]
Fair value of financial assets measured at fair value on a recurring basis					$ 0		$ 0
Receivables converted to preferred stock	$ 3,385,000
Preferred shares, initial dividend rate					12.00%
Preferred shares, subsequent dividend rate					20.00%
ZIOPHARM Oncology, Inc. \| Collaboration and licensing agreements
Related Party Transaction [Line Items]
Collaborative arrangement consideration received, number of preferred shares (in shares)			100,000
Revenues					$ 1,166,000	$ 5,377,000