INCOME TAX - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0	$ 0	$ 0
Unrecognized tax benefits	$ 3,200,000		3,200,000		$ 2,700,000
Accrued interest and penalties related to uncertain tax positions			$ 0		$ 0