MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Pfizer Inc. (Narrative) (Details) $ in Millions	1 Months Ended		73 Months Ended	80 Months Ended
	Dec. 31, 2017 USD ($) milestone	May 31, 2017 USD ($) milestone	Dec. 31, 2023 USD ($) milestone product	Dec. 31, 2023 USD ($) milestone
Pfizer Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement termination, term		15 years
Pfizer Inc. | S B Five Two Five and Other Products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement		$ 70.0
Potential amount to be funded for achievement of specified commercialized and sales milestones		266.5
Pfizer Inc. | S B Five Two Five and Other Products | Achievement of specified clinical development intellectual property and regulatory milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received		208.5
Pfizer Inc. | S B Five Two Five
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable		$ 220.0
Pfizer Inc. | License | Minimum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percentage of net sales per developed licensed product which will trigger royalties by counterparty	14.00%	14.00%
Pfizer Inc. | License | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Percentage of net sales per developed licensed product which will trigger royalties by counterparty	20.00%	20.00%
Pfizer Inc. | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement	$ 5.0
Collaborative arrangement, number of milestones achieved | milestone	1
Collaborative arrangement transaction price	$ 17.0
Pfizer Inc. | Other Products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable		$ 175.0
Pfizer SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement		55.0
Collaborative arrangement transaction price		134.0
Research service fees		$ 79.0
Pfizer SB-525 | S B Five Two Five and Other Products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaborative arrangement, number of milestones achieved | milestone		2		2
Milestone payments received				$ 55.0
Pfizer C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement termination, term	15 years
Milestone payments received	$ 12.0
Pfizer C9ORF72 | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement	12.0
Milestone payments received			$ 5.0
Number of products approved | product			0
Number of milestones included in transaction price | milestone			0
Pfizer C9ORF72 | C9ORF72 | Achievement of specified preclinical development clinical development and first commercial sale milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	60.0
Pfizer C9ORF72 | C9ORF72 | Achievement of commercial milestones | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	$ 90.0