Commitments and Contingencies - Additional Information (Detail)									1 Months Ended	3 Months Ended								12 Months Ended
	Nov. 12, 2015 USD ($)	Sep. 28, 2015 USD ($)	May. 22, 2015 USD ($)	Jan. 13, 2015 USD ($) shares	Jan. 09, 2015 USD ($) shares	Mar. 07, 2011 USD ($)	Jan. 06, 2011	Aug. 24, 2004 Patent	Jul. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) shares	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Agreement shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Dec. 31, 2012	Dec. 31, 2011 USD ($)	Mar. 31, 2016 $ / shares shares	May. 31, 2015 USD ($)	Oct. 29, 2013 $ / shares	Nov. 02, 2012 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Loss on disposal of fixed assets																				$ (585,000)
Total rent Expense																		$ 1,000,000	$ 1,200,000	1,000,000
Deferred rent - current portion										$ 348,000				$ 280,000				348,000	280,000
Deferred rent-non-current portion										313,000				570,000				313,000	570,000
Deferred rent liability net										661,000				850,000				661,000	850,000
Research and Development Expense																		106,785,000	32,706,000	42,852,000
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 million and no greater than $20 million per year.
Research and Development Service Agreement Aggregate Quarterly Payments																		11,250,000
Offset costs in research and development expense																		911,000
Deferred revenue - current portion										6,861,000				1,360,000				6,861,000	1,360,000
Deferred Revenue, long term										47,917,000								47,917,000
Sale of stock price per share | $ / shares																									$ 3.50
Research contract revenue										1,919,000	$ 1,869,000	$ 272,000	$ 272,000	340,000	$ 633,000	$ 200,000	$ 200,000	4,332,000	1,373,000	800,000
DEKK Tec Inc | Scenario, Forecast
Commitments and Contingencies Disclosure [Line Items]
Sale of stock price per share | $ / shares																							$ 0.02
Outstanding options to purchase common stock | shares																							13,808
Southern Research Institute
Commitments and Contingencies Disclosure [Line Items]
Royalty payment																		$ 25,000	25,000	25,000
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					$ 4,500,000
Number of products | Patent								2
Options to purchase common stock | shares																		50,222
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 expected to vest | shares														12,556					12,556
Solasia
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received						$ 5,000,000
Deferred revenue - current portion										272,000								$ 272,000
Research contract revenue																		$ 1,100,000
Estimated upfront payment for research and development funding earning period																		75 months
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
Novella Clinical, Inc.
Commitments and Contingencies Disclosure [Line Items]
Milestone maximum payment																										$ 790,000
Number of amendments signed | Agreement																		2
Novella Clinical, Inc. | Upon three clinical milestones
Commitments and Contingencies Disclosure [Line Items]
Installment payments													$ 10,000						$ 236,000
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
Predictive Therapeutics, Ltd.
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received																		250,000
Deferred revenue - current portion										200,000								200,000
Research contract revenue																		50,000
Predictive Therapeutics, Ltd. | Development Regulatory And Sales Based Milestone
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received	$ 250,000
Expected Additional milestone payments to be received																		12,800,000
License Agreement
Commitments and Contingencies Disclosure [Line Items]
Research and Development Expense																		$ 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																		$ 3,200,000
Deferred revenue, upfront payment										54,300,000								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
Prepaid Expenses and Other Current Assets
Commitments and Contingencies Disclosure [Line Items]
Pre paid research and development expenses										10,300,000								$ 10,300,000
Intrexon Corporation
Commitments and Contingencies Disclosure [Line Items]
Contract termination description																		The Company's obligation to pay 50% 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 | GVHDA Arrangement
Commitments and Contingencies Disclosure [Line Items]
Percent of company net profit																		50.00%
Contract termination description																		The Company's obligation to pay 50% of net profits or revenue with respect to these "retained" products will survive termination of the GvHD Agreement.
Licensing fee		$ 10,000,000
Agreement termination period		24 months
Agreement termination, notice period		90 days
Research and Development Expense																		$ 10,000,000
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]
Percent of company net profit							50.00%
Percentage of revenue agreed to pay which is obtained from sublicensor							50.00%
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																			2016-08
Loss on sublease																				42,000
Remaining contractual obligation																				367,000
Sublease revenue from subtenant			$ 105,000																	325,000
Loss on disposal of fixed assets																				(194,000)
Security deposits			$ 17,000							$ 127,000				$ 127,000				127,000	127,000	$ 20,000
Security deposit from subtenant														$ 20,000					$ 20,000
Boston, MA | The first floor
Commitments and Contingencies Disclosure [Line Items]
Loss on sublease																		$ 167,000