Commitments and Contingencies - Additional Information (Detail)								1 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 ($)	Sep. 30, 2015 USD ($)	Jul. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	May 22, 2015 USD ($)	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Dec. 31, 2012	Dec. 31, 2011 USD ($)	Mar. 31, 2016 USD ($)	May 31, 2015 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Total rent Expense											$ 300,000	$ 1,000,000		$ 1,200,000
Deferred rent - current portion											155,000	348,000
Deferred rent-non-current portion											126,000	313,000
Deferred rent liability net											281,000	661,000
Research and Development Expense											$ 157,791,000	106,785,000		32,706,000
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											$ 15,000,000	11,300,000
Offset costs in research and development expense											3,400,000
Deferred revenue - current portion											6,389,000	6,861,000
Deferred Revenue, long term											$ 41,528,000	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											250,000	250,000		$ 250,000
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
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	11,722,163
ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Agreement termination, notice period											90 days
Milestone payments, percentage											50.00%
Agreement commencement date											2015-05
Deferred revenue, revenue recognized											$ 6,400,000	$ 3,200,000
Deferred revenue, upfront payment											$ 47,900,000	$ 54,300,000							$ 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, stated value | $ / shares											$ 1,200	$ 1,200
Prepaid Expenses and Other Current Assets
Commitments and Contingencies Disclosure [Line Items]
Pre paid research and development expenses											$ 22,900,000
Development Milestone Payments | ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Payments for development, regulatory and commercial milestones per Product											60,000,000
Regulatory Milestone Payments | ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Payments for development, regulatory and commercial milestones per Product											148,000,000
Commercial Milestone Payments | ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Payments for development, regulatory and commercial milestones per Product											205,000,000
Substantive Milestones
Commitments and Contingencies Disclosure [Line Items]
Potential milestone payment											$ 15,000,000
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
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]
Issuance of common stock in licensing agreement, shares | shares	100,000										6,184
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
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				2016-08
Loss on sublease															42,000
Remaining contractual obligation															367,000
Sublease revenue from subtenant													$ 105,000		$ 325,000
Security deposits											$ 128,000	$ 128,000	$ 17,000
Sublease term amendment											Aug. 31, 2021
Security deposit from subtenant														$ 20,000
The first floor | Boston, MA
Commitments and Contingencies Disclosure [Line Items]
Loss on sublease												$ 167,000