SHARE-BASED COMPENSATION - Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares
Outstanding, beginning balance (in shares)	6.5
Granted (in shares)	0.0
Common stock—option exercises and restricted stock units vesting, net of shares withheld for employee taxes (in shares)	(1.0)
Forfeited, expired or canceled (in shares)	(0.3)
Outstanding, ending balance (in shares)	5.2	6.5
Weighted-Average Exercise Price
Outstanding, beginning balance, weighted-average exercise price (in dollars per share)	$ 2.36
Granted, weighted-average exercise price (in dollars per share)	0
Exercised, weighted-average exercise price (in dollars per share)	0.35
Forfeited, expired and canceled, weighted-average exercise price (in dollars per share)	6.04
Outstanding, ending balance, weighted-average exercise price (in dollars per share)	$ 2.56	$ 2.36
Outstanding, weighted-average remaining contractual term (in years)	5 years 10 months 20 days	6 years 1 month 13 days
Outstanding, aggregate intrinsic value	$ 2.9	$ 9.5
Exercised, aggregate intrinsic value	$ 1.8