MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Pfizer Inc. (Details)	1 Months Ended				12 Months Ended			13 Months Ended	49 Months Ended	68 Months Ended
	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2017 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) milestone product	Dec. 31, 2022 USD ($) royalty_fee milestone product
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues					$ 111,299,000	$ 110,701,000	$ 118,192,000
Pfizer SB-525
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement										$ 55,000,000
Collaborative arrangement transaction price										134,000,000
Research service fees										$ 79,000,000
Revenues					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
Milestone payments received										$ 55,000,000
Number of products approved | product										0
Number of milestones included in transaction price | royalty_fee										0
Pfizer, Giroctocogene Fitelparvovec
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement		$ 25,000,000
Revenues					0	0	34,449,000
Collaborative arrangement, increase (decrease) in revenue							2,400,000
Collaborative arrangement, decrease in net loss							$ 2,400,000
Collaborative arrangement, net loss per share (in dollars per share) | $ / shares							$ 0.02
Pfizer, Giroctocogene Fitelparvovec | Phase Three Clinical Trial
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received	$ 30,000,000
Cumulative compensation earned							$ 30,000,000	$ 30,000,000
Pfizer, Giroctocogene Fitelparvovec | Amended collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognition of milestone							1,300,000	$ 25,000,000
Pfizer, Giroctocogene Fitelparvovec | License and Service
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues					0	0	3,111,000
Pfizer, Giroctocogene Fitelparvovec | Milestone achievement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues					0	0	31,338,000
Pfizer Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement termination, term				15 years
Collaborative arrangement, increase (decrease) in revenue							8,800,000
Collaborative arrangement, decrease in net loss							$ 8,800,000
Collaborative arrangement, net loss per share (in dollars per share) | $ / shares							$ 0.06
Pfizer Inc. | S B Five Two Five And Other Products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement				$ 70,000,000
Potential amount to be funded for achievement of specified commercialized and sales milestones				266,500,000
Milestone revenue receivable				300,000,000
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				208,500,000
Pfizer Inc. | S B Five Two Five And Other Products | Achievement of first commercial sale milestones
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and sales-based milestone payments to be received				$ 475,000,000
Pfizer Inc. | License and Service | 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 and Service | 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			$ 5,000,000				$ 5,000,000
Development and sales-based milestone payments to be received	$ 5,000,000
Collaborative arrangement transaction price			$ 17,000,000
Pfizer Inc. | Other products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Milestone revenue receivable				$ 175,000,000
Pfizer C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Agreement termination, term			15 years
Milestone payments received			$ 12,000,000						$ 5,000,000
Number of products approved | product									0
Number of milestones included in transaction price | milestone									0
Revenues					0	0	12,985,000
Pfizer C9ORF72 | License and Service
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues					0	0	7,985,000
Pfizer C9ORF72 | Milestone achievement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues					0	0	$ 5,000,000
Pfizer C9ORF72 | C9ORF72
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues under agreement			12,000,000
Revenues					$ 0	$ 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			60,000,000
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			$ 90,000,000