Commitments and Contingencies - Additional Information (Detail) $ in Thousands					1 Months Ended		3 Months Ended		12 Months Ended
	Oct. 05, 2018 USD ($)	Jan. 13, 2015 USD ($)	May 07, 2011 USD ($)	Mar. 07, 2011 USD ($)	Jul. 31, 2015 USD ($)	Aug. 24, 2004 Patent	Mar. 31, 2019 USD ($) shares	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017	Feb. 19, 2019 USD ($)	Jan. 30, 2018 ft²	Mar. 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Research and development expense							$ 9,476	$ 10,183	$ 1,000
Research and development arrangement Terms										Pursuant to the Research and Development Agreement, the Company, Precigen and MD Anderson have agreed to form a joint steering committee that will oversee and manage the new and ongoing research programs. Under the License Agreement with Precigen, the Company and Precigen agreed that Precigen would no longer participate on the joint steering committee after the date of the License Agreement. As provided under the MD Anderson License, the Company provided 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.
Cash balance							51,487	51,108	$ 61,729
Agreement commencement date										2015-05
Reimbursement of historical costs	$ 1,000
MD Anderson License and the Research and Development Agreement Member [Member]
Commitments and Contingencies Disclosure [Line Items]
Research and development service agreement aggregate quarterly payments							1,400
Cash resources on hand							26,400
CRADA Agreement [Member]
Commitments and Contingencies Disclosure [Line Items]
Obligations due under contract											$ 5,000
Remaining contractual obligation											$ 6,900
Quarterly payments under contract							$ 625	625
Gorilla IL12 Products [Member] | Parent [Member]
Commitments and Contingencies Disclosure [Line Items]
Percentage of development costs	80.00%
Percentage of operating profits	80.00%
CAR Products [Member]
Commitments and Contingencies Disclosure [Line Items]
Amount of royalties receivable	$ 50,000
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
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 | Research and Development Expense
Commitments and Contingencies Disclosure [Line Items]
Issuance of common stock in a license agreement							$ 87
Solasia
Commitments and Contingencies Disclosure [Line Items]
Upfront payment received			$ 5,000	$ 5,000
Milestone payment received													$ 1,000
Milestone Payments Payable													$ 1,000
Solasia | Development-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received							32,500
Solasia | Sales-based milestones
Commitments and Contingencies Disclosure [Line Items]
Expected Additional milestone payments to be received							$ 53,500
ARES Trading License
Commitments and Contingencies Disclosure [Line Items]
Research and development expense								$ 1,600
Agreement termination, notice period							90 days
Prepaid Expenses and Other Current Assets | MD Anderson License
Commitments and Contingencies Disclosure [Line Items]
Cash balance							$ 19,800
Other Noncurrent Assets | MD Anderson License and the Research and Development Agreement Member [Member]
Commitments and Contingencies Disclosure [Line Items]
Cash resources on hand							6,600
Other Noncurrent Assets | MD Anderson License
Commitments and Contingencies Disclosure [Line Items]
Cash balance							$ 6,600
Intrexon Corporation
Commitments and Contingencies Disclosure [Line Items]
Licensing fee					$ 115,000
Milestone payment receivable period							2 years
Upfront payment received					$ 57,500
Percentage of upfront fee Payable					50.00%
Annual Licensing fee	100
Reimbursement of historical costs	1,000
Expected additional milestones payable	$ 52,500
Intrexon Corporation | Gorilla IL12 Products [Member]
Commitments and Contingencies Disclosure [Line Items]
Percentage of development costs	20.00%
Percentage of operating profits	20.00%
Intrexon Corporation | T-cell receptor
Commitments and Contingencies Disclosure [Line Items]
Maximum royalty amount	$ 100,000
Portion of income payable to related party	20.00%
Minimum | MD Anderson License and the Research and Development Agreement Member [Member]
Commitments and Contingencies Disclosure [Line Items]
Research and development expense		$ 15,000
Maximum | MD Anderson License and the Research and Development Agreement Member [Member]
Commitments and Contingencies Disclosure [Line Items]
Research and development expense		$ 20,000
Houston, TX
Commitments and Contingencies Disclosure [Line Items]
Operating lease area | ft²												210