NET REVENUES FROM COLLABORATIONS - Additional Information (Detail)			1 Months Ended			3 Months Ended
	Mar. 31, 2020 USD ($)	Apr. 08, 2019 USD ($) program	Mar. 31, 2020 USD ($) shares	Jan. 31, 2019 $ / shares shares	Oct. 31, 2017 USD ($) shares	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock, net of offering costs (in shares) | shares				5,000,000
Offering proceeds, net of costs						$ 0	$ 381,900,000
Common stock at a price per share (in dollars per share) | $ / shares				$ 77.50
Vir Biotechnology
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fee received					$ 10,000,000.0
Shares of Vir common stock (in shares) | shares					1,111,111
Milestone shares earned (in shares) | shares			1,111,111
Milestone payment earned			$ 15,000,000.0
Agreement termination period						90 days
Transaction Price Allocated						$ 105,200,000
Transactional price remaining performance obligation	$ 71,800,000		71,800,000			71,800,000
Global Strategic Collaboration | Regeneron
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fee received		$ 400,000,000.0
Transaction Price Allocated	555,100,000					521,600,000
Transactional price remaining performance obligation	$ 296,800,000		$ 296,800,000			$ 296,800,000
Discovery period of programs development		5 years
Extended additional discovery period of programs development		2 years
Maximum royalties and commercial milestone payments upon potential product sale		$ 325,000,000.0
Maximum additional milestone payments to be receive upon achievement of certain criteria		$ 200,000,000.0
Number of targeted programs | program		30
Maximum percentage of royalty payments		20.00%
Global Strategic Collaboration | Regeneron | Funding At Program Initiation
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement		$ 2,500,000
Global Strategic Collaboration | Regeneron | Funding At Lead Candidate Identification
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement		2,500,000
Global Strategic Collaboration | Regeneron | Funding At Steady State
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential proceeds from collaboration arrangement		30,000,000.0
Global Strategic Collaboration | Regeneron | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research term extension fee		400,000,000.0
Collaborative arrangement milestone payments		$ 150,000,000.0
Royalty rate		20.00%