NET REVENUES FROM COLLABORATIONS - Additional Information (Detail)			1 Months Ended					3 Months Ended		9 Months Ended		104 Months Ended
	Sep. 30, 2021 USD ($) candidate	Jul. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) shares	Apr. 30, 2019 USD ($) program	Oct. 31, 2017 USD ($) shares	Feb. 28, 2013 USD ($)	Sep. 30, 2021 USD ($) candidate	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) candidate	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) candidate
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract with customer liability revenue recognized								$ 12,700,000	$ 19,200,000	$ 65,200,000	$ 50,700,000
Increase (decrease) in research and development expense								(3,300,000)	$ (3,200,000)	$ (12,700,000)	$ (8,400,000)
Vir Biotechnology
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fee received						$ 10,000,000
Agreement termination period										90 days
Transaction price	$ 110,800,000
Transactional price remaining performance obligation	$ 44,400,000							$ 44,400,000		$ 44,400,000		$ 44,400,000
Milestone payment earned			$ 10,000,000	$ 15,000,000
Shares of Vir common stock (in shares) | shares						1,111,111
Milestone shares earned (in shares) | shares				1,111,111
Additional development candidates to be delivered | candidate	4							4		4		4
Global Strategic Collaboration | Regeneron Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discovery period of programs development					5 years
Extended additional discovery period of programs development					5 years
Maximum royalties and commercial milestone payments upon potential product sale					$ 325,000,000
Upfront fee received					400,000,000
Maximum additional milestone payments to be receive upon achievement of certain criteria					$ 200,000,000
Number of targeted programs | program					30
Agreement termination period					90 days
Maximum percentage of royalty payments					20.00%
Transaction price	$ 539,700,000									$ 521,600,000
Change in transaction price										7,900,000
Transactional price remaining performance obligation	$ 161,500,000							$ 161,500,000		$ 161,500,000		$ 161,500,000
Global Strategic Collaboration | Funding At Program Initiation | Regeneron Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement					$ 2,500,000
Global Strategic Collaboration | Funding At Lead Candidate Identification | Regeneron Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement					2,500,000
Global Strategic Collaboration | Funding At Steady State | Regeneron Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement					30,000,000
Global Strategic Collaboration | Maximum | Regeneron Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research term extension fee					400,000,000
Collaborative arrangement milestone payments					$ 150,000,000
Royalty rate					20.00%
Product Alliances | Novartis AG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment earned												$ 45,000,000
Maximum amount of potential future milestones							$ 135,000,000
Future payments on achievement of specified regulatory milestones							25,000,000
Future payments on achievement of other specified regulatory milestones							10,000,000
Future payments on achievement of specified commercialization milestones							$ 100,000,000
Product Alliances | Minimum | Novartis AG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty rate	10.00%							10.00%		10.00%		10.00%
Product Alliances | Maximum | Novartis AG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty rate	20.00%							20.00%		20.00%		20.00%
PeptiDream, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment		$ 10,000,000						$ 10,000,000
Maximum milestone payments		$ 247,000,000