Commitments and Contingencies - Additional Information (Detail) - USD ($)				1 Months Ended	12 Months Ended
	May 28, 2019	May 11, 2017	Jan. 13, 2015	Jul. 31, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2021	Nov. 28, 2020	Oct. 22, 2019	Feb. 19, 2019	Nov. 11, 2018	Oct. 05, 2018	May 31, 2016	Dec. 31, 2014	Aug. 24, 2004
Accrued Payments
Research and development expense					$ 38,331,000	$ 34,134,000	$ 45,084,000
Cash balance					79,741,000	61,729,000	$ 70,946,000
Agreement commencement date							2015-05
Number of Warrants												18,939,394
MD Anderson License and the Research and Development Agreement Member [Member]
Accrued Payments
Research and development service agreement aggregate quarterly payments					0	2,700,000
Reimbursement of historical costs										$ 20,000,000
Accrued Payments										3,000,000
Number of Warrants								3,333,333
Aggregate potential benchmark payments										$ 36,500,000
CRADA Agreement [Member]
Accrued Payments
Obligations due under contract											$ 5,000,000
Quarterly payments under contract					$ 2,500,000
License Agreement with the National Cancer Institute [Member]
Accrued Payments
Expected cash payment payable per installments	$ 500,000
The University of Texas MD Anderson Cancer Center and The Texas A & M University System
Accrued Payments
Milestone maximum payment																$ 4,500,000
Options to purchase common stock					50,222
Shares vested					37,666
The University of Texas MD Anderson Cancer Center and The Texas A & M University System | Research and Development Expense
Accrued Payments
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
Accrued Payments
Shares vested															12,556
Solasia
Accrued Payments
Upfront payment received		$ 5,000,000
Milestone payment received														$ 1,000,000
Milestone Payments Payable														$ 1,000,000
ARES Trading License
Accrued Payments
Research and development expense						$ 100,000	$ 1,600,000
License Agreement with the National Cancer Institute [Member]
Accrued Payments
Reimbursement of historical costs	46,000
Expected Cash Payment Payable	1,500,000				500,000
Minimum Royalties Amount Payable	$ 300,000
Description Of First Annual Royalty Payable	The first minimum annual royalty payment is payable on the date that is eighteen months following the date of the Patent License.
Description Of First Benchmark Payable	The first benchmark payment of $0.1 million will be due upon the initiation of the Company’s first sponsored phase 1 clinical trial of a licensed product or licensed process in the field of use licensed under the Patent License.
Description Of option To terminate Agreement	The NCI may terminate or modify the Patent License in the event of a material breach, including if the Company does not meet certain milestones by certain dates, or upon certain insolvency events that remain uncured following the date that is 90 days following written notice of such breach or insolvency event.
Agreement termination, notice period	60 days
payments under the Patent License	$ 600,000				1,000,000
License Agreement with the National Cancer Institute [Member] | Performance Based Payments Member [Member]
Accrued Payments
Aggregate Benchmark Payments Payable	4,300,000
License Agreement with the National Cancer Institute [Member] | One Time Benchmark Payments [Member]
Accrued Payments
Potential Benchmark Payments Payable	12,000,000
License Agreement with the National Cancer Institute [Member] | Scenario, Forecast [Member]
Accrued Payments
Expected Cash Payment Payable									$ 1,500,000
Minimum Royalties Amount Payable									$ 100,000
License Agreement with the National Cancer Institute [Member] | Post Marketing Approval [Member] | Performance Based Payments Member [Member]
Accrued Payments
Aggregate Benchmark Payments Payable	3,000,000
License Agreement with the National Cancer Institute [Member] | licensed products [Member] | One Time Benchmark Payments [Member]
Accrued Payments
Maximum Sales Revenue On Which Benchmark Payments Payable	$ 1,000,000,000
Prepaid Expenses and Other Current Assets
Accrued Payments
Prepaid Patent					300,000
Prepaid Expenses and Other Current Assets | MD Anderson License
Accrued Payments
Cash balance					20,300,000
Intrexon Corporation
Accrued Payments
Licensing fee				$ 115,000,000
Research and development expense					$ 1,000,000
Upfront payment received				$ 57,500,000
Percentage of upfront fee Payable				50.00%
Reimbursement of historical costs													$ 1,000,000
Minimum [Member] | MD Anderson License and the Research and Development Agreement Member [Member]
Accrued Payments
Research and development expense			$ 15,000,000
Maximum [Member] | MD Anderson License and the Research and Development Agreement Member [Member]
Accrued Payments
Research and development expense			$ 20,000,000