FAIR VALUE MEASUREMENTS - UNREALIZED GAIN (LOSS) ON INVESTMENTS (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Net unrealized losses included in earnings related to investments held at end of period	$ 0.1
Net unrealized gains included in earnings related to investments held at end of period		$ 5.7	$ 9.7	$ 2.9