MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Biogen MA, Inc. (Details) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	May 31, 2020 USD ($)	Apr. 30, 2020 USD ($) product_target $ / shares shares	Dec. 31, 2022 USD ($) material_right product_target	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Accounts receivable			$ 3,678	$ 6,013
General and administrative expense			$ 62,682	63,219	$ 67,097
Biogen MA, Inc. | License and Service
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fixed consideration		$ 204,600
Number of material rights expired | material_right			1
Number of material rights outstanding | material_right			7
Remaining performance obligation amount			$ 151,300	182,200
General and administrative expense			400	600	400
Biogen MA, Inc. | Stock Purchase Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares		24,420,157
Sale of stock, price per share (in dollars per share) | $ / shares		$ 9.2137
Consideration received from sale of stock		$ 225,000
Agreement restriction expiration period		3 years
Agreement restriction, ownership percentage (less than)		5.00%
Sale of stock, excess consideration received on transaction		$ 79,600
Collaboration agreement, equity issued		145,400
Accounts receivable			500	2,800
Deferred revenue			$ 132,200	$ 154,000
Net pension losses					2,900
Biogen MA, Inc. | Collaboration and license agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from collaborators	$ 125,000	125,000
Maximum milestone payment receivable		$ 2,400,000
Number of additional neurological disease gene targets | product_target		7
Target selection period		5 years
Number of product targets selected | product_target		3
Collaborative arrangement, maximum number of product targets to replace | product_target			8
Collaboration arrangement, commission fee, portion of gross proceeds, value					$ 7,000
Collaborative agreement, percent of initial recognition		2.00%
Contract with customer, asset, after allowance for credit Loss			$ 4,100
Biogen MA, Inc. | Collaboration and license agreement | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration arrangement, research period		7 years
Biogen MA, Inc. | Collaboration and license agreement | Pre-approval Milestone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payment receivable		$ 925,000
Biogen MA, Inc. | Collaboration and license agreement | Sales-based Milestone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Maximum milestone payment receivable		$ 1,500,000