MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Astellas Gene Therapies, Inc. (Narrative) (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2024 USD ($) target indication	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($) target indication
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues		$ 39,552	$ 57,800
Deferred revenues	$ 7,556	899	7,556
Deferred revenues, non-current	$ 5,874	5,874	$ 5,874
Astellas Gene Therapies, Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty obligation, term (in years)	10 years
Astellas Gene Therapies, Inc. | License
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of additional targets | target	4		4
Number of indications per target | indication	3		3
Agreement term (in years)	3 years
Contract with customer liability	$ 20,000		$ 20,000
Variable consideration amount	$ 1,300,000		$ 1,300,000
Number of targets | target	5		5
Astellas Gene Therapies, Inc. | Initial License
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer liability	$ 6,500		$ 6,500
Revenues	6,500	$ 7,600
Astellas Gene Therapies, Inc. | Additional License
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer liability	$ 13,500		$ 13,500
Underlying options, exercise or expiration term (in years)		3 years
Deferred revenues, non-current		$ 5,900