FAIR VALUE MEASUREMENTS - UNREALIZED GAIN (LOSS) ON INVESTMENTS (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Net unrealized gains included in earnings related to investments held at end of period	$ 5.8	$ 11.4	$ 9.8
Net unrealized losses included in earnings related to investments held at end of period				$ 2.8