Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended									12 Months Ended			49 Months Ended
	Dec. 31, 2016	Oct. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Nov. 30, 2015	Jul. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 28, 2015
Related Party Transaction [Line Items]
Shares issued as compensation for services										$ 10,777,000	$ 2,169,000	$ 486,000
Fair value of assets	$ 335,307,000									335,307,000	291,762,000
Other nonoperating income										1,700,000	1,314,000	(168,000)
Purchases of equity securities and warrants										2,308,000	17,080,000	19,496,000
Third Security, LLC
Related Party Transaction [Line Items]
Expense for services										$ 309,000	$ 428,000	$ 291,000
Services agreement, term		2 months			1 year
Shares issued as compensation for services, shares										337,163	48,678
Shares issued as compensation for services										$ 8,571,000	$ 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				2,261,419
Price per share of common shares (in usd per share)				$ 0.52
Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Payments to acquire convertible notes and warrants			$ 2,604,000
Common stock purchased from collaborative partners, shares						375,868
Price per share of common shares (in usd per share)						$ 5.80
AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Common stock purchased from collaborative partners, shares							278,788
Warrants purchased from collaborative partners, 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								1,772,364
Price per share of common shares (in usd per share)											$ 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
Harvest Intrexon Enterprise Fund I, LP
Related Party Transaction [Line Items]
Other nonoperating income										2,483,000	$ 1,349,000
Common Stock | Third Security, LLC
Related Party Transaction [Line Items]
Expense for services					$ 800,000
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
Other assets | Convertible note and warrants | Fibrocell Science, Inc.
Related Party Transaction [Line Items]
Fair value of assets	$ 1,642,000									$ 1,642,000
Third Security, LLC | Chief Executive Officer
Related Party Transaction [Line Items]
Ownership interest	100.00%									100.00%
AmpliPhi Biosciences Corporation
Related Party Transaction [Line Items]
Realized investment gain (loss)	$ (4,098,000)