MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 29,378	$ 27,872	$ 57,609	$ 54,152
Novartis Institutes for BioMedical Research, Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	10,928	9,581	19,823	17,442
Novartis Institutes for BioMedical Research, Inc. | Recognition of upfront fee
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	8,622	7,559	15,640	13,759
Novartis Institutes for BioMedical Research, Inc. | Research services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	2,306	2,022	4,183	3,683
Biogen MA, Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	10,052	10,767	21,245	21,217
Biogen MA, Inc. | Recognition of upfront fee
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	7,306	7,306	14,612	14,612
Biogen MA, Inc. | Research services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	2,746	3,461	6,633	6,605
Kite Pharma, Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	6,334	6,324	12,642	12,612
Kite Pharma, Inc. | Recognition of upfront fee
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	6,227	6,227	12,386	12,386
Kite Pharma, Inc. | Research services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	107	97	256	226
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	1,761	957	3,260	2,017
Sanofi | Recognition of upfront fee
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	366	206	677	433
Sanofi | Research services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	1,148	613	2,126	1,292
Sanofi | Milestone achievement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 247	$ 138	$ 457	$ 292