Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Nov. 30, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Shares issued as payment for services					$ 2,299,000	$ 2,917,000	$ 7,987,000	$ 8,404,000
Noncash dividend income							38,000	14,575,000
Fair value of financial assets measured at fair value on a recurring basis					64,233,000		64,233,000		$ 122,181,000
Revenues					23,043,000	32,448,000	82,364,000	117,389,000
Third Security, LLC
Related Party Transaction [Line Items]
Initial term of services agreement				1 year
Expense for services					$ 8,000	$ 16,000	$ 26,000	$ 33,000
Shares issued as payment for services (in shares)					340,453	166,143	1,180,446	466,460
Shares issued as payment for services					$ 1,855,000	$ 2,417,000	$ 6,217,000	$ 6,522,000
Sublease rental income					$ 22,000		$ 66,000	66,000
Third Security, LLC | Common Stock
Related Party Transaction [Line Items]
Expense for services				$ 800,000
Histogenics Corporation, OvaScience Inc., and Synthetic Biologics Inc.
Related Party Transaction [Line Items]
Revenues								$ 3,183,000	11,877,000
Third Security, LLC | Chief Executive Officer
Related Party Transaction [Line Items]
Ownership interest					100.00%		100.00%
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
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]
Collaborative arrangement consideration received, number of preferred shares (in shares)			100,000
Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Purchases of preferred stock and warrants		$ 1,161,000
Fibrocell Science, Inc. | Preferred stock | Other Noncurrent Assets
Related Party Transaction [Line Items]
Fair value of financial assets measured at fair value on a recurring basis					$ 390,000		$ 390,000		191,000
ZIOPHARM Oncology, Inc.
Related Party Transaction [Line Items]
Dividend income, number of preferred shares received (in shares)						3,847		11,205
Noncash dividend income						$ 4,649,000		$ 14,539,000
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					253,000		253,000		120,000
Oragenics, Inc. | Preferred stock
Related Party Transaction [Line Items]
Fair value of financial assets measured at fair value on a recurring basis					$ 0		$ 0		$ 0
Receivables converted to preferred stock	$ 3,385,000
Preferred shares, initial dividend rate							12.00%
Preferred shares, subsequent dividend rate							20.00%