LEASES - Narrative (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) location	Dec. 31, 2020 USD ($)
Leases [Abstract]
Number of office space locations leased under operating leases | location	2
Operating lease terms (in years)	5 years
Operating lease cash payments | $	$ 0.5	$ 1.0