Commitments and Contingencies - Additional Information (Detail)								1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 29, 2016 $ / shares shares	Sep. 28, 2015 USD ($)	Jan. 13, 2015 USD ($) shares	Jan. 09, 2015 USD ($) shares	Mar. 07, 2011 USD ($)	Jan. 06, 2011	Aug. 24, 2004 Patent	Nov. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jul. 31, 2015 USD ($)	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2013 USD ($)	Dec. 31, 2012	Dec. 31, 2011 USD ($)	Mar. 31, 2016 USD ($)	May 31, 2015 USD ($)	Dec. 31, 2014 USD ($) shares
Commitments and Contingencies Disclosure [Line Items]
Loss on disposal of fixed assets															$ 1,000
Total rent Expense												$ 109,000	$ 104,000	$ 231,000	581,000
Deferred rent - current portion												177,000		177,000		$ 348,000
Deferred rent-non-current portion												163,000		163,000		313,000
Deferred rent liability net												340,000		340,000		661,000
Research and Development Expense												8,975,000	$ 16,970,000	$ 148,402,000	98,643,000
Research and development arrangement Terms														Pursuant to the Research and Development Agreement, the Company, Intrexon and MD Anderson have agreed to form a joint steering committee that will oversee and manage the new and ongoing research programs. As provided under the MD Anderson License, the Company will provide funding for research and development activities in support of the research programs under the Research and Development Agreement for a period of three years and in an amount of no less than $15.0 million and no greater than $20.0 million per year.
Research and Development Service Agreement Aggregate Quarterly Payments														$ 3,800,000
Offset costs in research and development expense														2,700,000
Research and Development Service Agreement Aggregate Payments														22,500,000
Deferred revenue - current portion												6,389,000		6,389,000		6,861,000
Deferred Revenue, long term												43,125,000		$ 43,125,000		47,917,000
Issuance of common stock in a license agreement															67,285,000
The University of Texas MD Anderson Cancer Center and The Texas A & M University System
Commitments and Contingencies Disclosure [Line Items]
Milestone maximum payment																						$ 4,500,000
Number of products | Patent							2
Options to purchase common stock | shares														50,222
Shares vested | shares																						37,666
The University of Texas MD Anderson Cancer Center and The Texas A & M University System | Research and Development Expense
Commitments and Contingencies Disclosure [Line Items]
Issuance of common stock in a license agreement														$ 87,000
The University of Texas MD Anderson Cancer Center and The Texas A & M University System | Upon enrollment of the first patient in a multi-center pivotal clinical trial
Commitments and Contingencies Disclosure [Line Items]
Shares vested | shares																						12,556
Solasia
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received					$ 5,000,000
Milestone payment received																				$ 1,000,000
Milestone Payments Payable																				$ 1,000,000
Solasia | Development-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received														32,500,000
Solasia | Sales-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received														53,500,000
Baxter Healthcare Corporation | Upon the successful U.S. IND application for indibulin
Commitments and Contingencies Disclosure [Line Items]
Installment payments														0	$ 0
Baxter Healthcare Corporation | Upon the successful U.S. IND application for indibulin | Scenario, Forecast
Commitments and Contingencies Disclosure [Line Items]
Additional payment payable amount								$ 250,000	$ 250,000
License Agreement
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense														$ 67,300,000		$ 67,300,000
Issuance of common stock in licensing agreement, shares | shares														11,722,163		11,722,163
ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Agreement termination, notice period														90 days
Payments for development and commercial milestones per Product														$ 413,000,000
Milestone payments, percentage														50.00%
Agreement commencement date														2015-05
Deferred revenue, revenue recognized												1,600,000		$ 4,800,000
Deferred revenue, upfront payment												$ 49,500,000		$ 49,500,000							$ 57,500,000
Minimum
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense			$ 15,000,000
Maximum
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense			20,000,000
Series 1 Preferred Stock
Commitments and Contingencies Disclosure [Line Items]
Preferred stock, shares issued | shares												103,063		103,063		0
Preferred stock, stated value | $ / shares												$ 1,200		$ 1,200		$ 1,200
Issuance of common stock in licensing agreement, shares | shares														100,000
Prepaid Expenses and Other Current Assets
Commitments and Contingencies Disclosure [Line Items]
Pre paid research and development expenses												$ 19,800,000		$ 19,800,000
Intrexon Corporation
Commitments and Contingencies Disclosure [Line Items]
Contract termination description														The Company's obligation to pay 20% of net profits or revenue described above with respect to these "retained" products will survive termination of the Channel Agreement.
Licensing fee		$ 10,000,000									$ 115,000,000
Milestone payment receivable														$ 5,000,000
Milestone payment receivable period														2 years
Upfront payment received											$ 57,500,000
Percentage of upfront fee Payable											50.00%
Milestone maximum payment												$ 50,000,000		$ 50,000,000
Intrexon Corporation | 2016 GvHD Amendment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit														20.00%
Contract termination description														The Company's obligation to pay 20% of net profits or revenue with respect to these "retained" products will survive termination of the GvHD Agreement.
Licensing fee		$ 10,000,000
Research and Development Expense										$ 10,000,000
Agreement termination period		24 months
Agreement termination, notice period		90 days
Intrexon Corporation | License Agreement
Commitments and Contingencies Disclosure [Line Items]
Cash consideration for license agreement			$ 50,000,000
Intrexon Corporation | Letter Agreement
Commitments and Contingencies Disclosure [Line Items]
Cash consideration for license agreement				$ 7,500,000
Intrexon Corporation | Quarterly Payment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit						20.00%
Percentage of revenue agreed to pay which is obtained from sublicensor						50.00%
Intrexon Corporation | Quarterly Payment | 2016 GvHD Amendment | After Amendment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit	20.00%
Intrexon Corporation | Quarterly Payment | 2016 GvHD Amendment | Before Amendment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit	50.00%
Intrexon Corporation | Quarterly Payment | ECP Channel Agreement | After Amendment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit	20.00%
Intrexon Corporation | Quarterly Payment | ECP Channel Agreement | Before Amendment
Commitments and Contingencies Disclosure [Line Items]
Royalty percentage of net profit	50.00%
Intrexon Corporation | Series 1 Preferred Stock
Commitments and Contingencies Disclosure [Line Items]
Preferred stock, shares issued | shares	100,000											3,063		3,063
Preferred stock, stated value | $ / shares	$ 1,200
ZIOPHARM | License Agreement
Commitments and Contingencies Disclosure [Line Items]
Common stock issued for cash | shares			10,124,561
Cash consideration for license agreement			$ 50,000,000
ZIOPHARM | Letter Agreement
Commitments and Contingencies Disclosure [Line Items]
Common stock issued for cash | shares				1,597,602
Cash consideration for license agreement				$ 7,500,000
New York, NY
Commitments and Contingencies Disclosure [Line Items]
Letter of credit												$ 388,000		$ 388,000					$ 388,000
Operating lease expiration month and year																		2018-10
Loss on sublease																	$ 729,000
Remaining contractual obligation																	2,300,000
Sublease revenue from subtenant																	1,600,000
Loss on disposal of fixed assets																	$ (392,000)
Boston, MA
Commitments and Contingencies Disclosure [Line Items]
Operating lease expiration month and year																			2016-08
Security deposits												$ 128,000		$ 128,000		$ 128,000
Sublease term amendment														Aug. 31, 2021