MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 13,076	$ 8,071
Kite Pharma Inc
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	7,219	8,312
Kite Pharma Inc | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	6,227	6,159
Kite Pharma Inc | Research Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	992	2,153
Pfizer SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	3,183	(3,040)
Pfizer SB-525 | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	2,190	(3,040)
Pfizer SB-525 | Milestone Achievement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	993	0
Pfizer | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	360	615
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	499	1,949
Sanofi | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	(729)	752
Sanofi | Research Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	1,720	1,197
Sanofi | Milestone Achievement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ (492)	$ 0