MAJOR CUSTOMERS, PARTNERSHIPS AND STRATEGIC ALLIANCES - Biogen MA, Inc. (Detail) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
	May 31, 2020 USD ($)	Apr. 30, 2020 USD ($) product_target $ / shares shares	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Accounts receivable			$ 6,002			$ 6,002			$ 6,013
Biogen MA, Inc. | Stock purchase agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
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 on transaction		$ 225,000
Standstill restriction period		3 years
Standstill restriction, ownership threshold percentage ownership percentage		5.00%
Collaborative arrangement transaction price		$ 204,600
Excess consideration received on transaction		79,600
Collaboration agreement, equity issued		145,400
Accounts receivable			2,300			2,300			2,800
Deferred revenue			139,400			139,400			$ 154,000
Recognized portion of equity issued								$ 2,900
Biogen MA, Inc. | Collaboration And License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Consideration received on transaction		204,600
Proceeds from collaborators	$ 125,000	125,000
Maximum milestone payment receivable		$ 2,400,000
Number of product targets | product_target		12
Number of additional product targets | product_target		8
Target selection period		5 years
Number of product targets selected | product_target		3
Research period		7 years
Maximum number of product targets replaced | product_target		10
Financial advisory fees								$ 7,000
Percent of initial recognition		2.00%			2.00%			2.00%
Portion of contract asset recognized			4,100			4,100
Amortization			$ 100	$ 200		$ 300	$ 300
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