Related Party Transactions - Additional Information (Detail)		1 Months Ended							12 Months Ended			49 Months Ended
	Aug. 07, 2015	Jul. 31, 2015 $ / shares shares	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) $ / shares shares	Sep. 30, 2014 USD ($)	Nov. 30, 2013 $ / shares shares	Sep. 30, 2013 $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($)	Feb. 28, 2015 USD ($)
Related Party Transaction [Line Items]
Services agreement, term									1 year
Shares issued as compensation for services									$ 2,169,000	$ 486,000	$ 124,000
Purchases of equity securities and warrants									17,080,000	19,496,000	28,650,000
Fair value of assets					$ 280,497,000				291,762,000	280,497,000
Collaboration and licensing revenues									87,821,000	45,212,000	23,525,000
Upfront and milestone payments
Related Party Transaction [Line Items]
Collaboration and licensing revenues									32,513,000	9,625,000	6,944,000
Third Security, LLC
Related Party Transaction [Line Items]
Expense for services									$ 428,000	$ 291,000	455,000
Shares issued as compensation for services, shares | shares									48,678
Shares issued as compensation for services									$ 1,375,000
ZIOPHARM Oncology, Inc.
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, value												$ 43,582,000
Oragenics, Inc.
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares | shares								1,300,000
Price per share of common shares, in usd per share | $ / shares								$ 3.00
Maximum percentage of shares of future securities offerings of collaborative partners to which the entity is entitled to purchase									30.00%
Oragenics ECC 3
Related Party Transaction [Line Items]
Commitment period for purchase of additional common stock after effective date			16 months
Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares | shares		375,868
Price per share of common shares, in usd per share | $ / shares		$ 5.80
AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares | shares				278,788
Warrants purchased from collaborative partners, shares | shares				69,696
Purchases of equity securities and warrants				$ 2,300,000
Histogenics Corporation
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares | shares					1,772,364
Price per share of common shares, in usd per share | $ / shares					$ 11.00					$ 11.00
Note receivable interest rate						6.00%
Histogenics Corporation | Upfront and milestone payments | Upfront
Related Party Transaction [Line Items]
Collaborative agreement, consideration received, value of convertible promissory note						$ 10,000,000
Related Parties, Aggregated
Related Party Transaction [Line Items]
Collaboration and licensing revenues									$ 77,354,000	$ 41,030,000	$ 22,783,000
Common Stock | Third Security, LLC
Related Party Transaction [Line Items]
Expense for services									800,000
Share Purchase Rights Plan | Oragenics, Inc.
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares | shares							1,100,000
Price per share of common shares, in usd per share | $ / shares							$ 2.50
Warrants | AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Purchases of equity securities and warrants				321,000
Common Stock | AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Purchases of equity securities and warrants				$ 1,979,000
AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Reverse stock split ratio	1-for-50
Reverse stock split, conversion ratio	0.02
Other assets | Warrants | AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Fair value of assets									134,000
Maximum | Oragenics, Inc.
Related Party Transaction [Line Items]
Purchase of additional common stock			$ 10,000,000
Other nonoperating income | Harvest Intrexon Enterprise Fund I, LP
Related Party Transaction [Line Items]
Management fees revenue									$ 1,349,000