EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net (loss) income	$ (33.0)	$ (736.8)	$ (120.1)	$ (80.0)	$ (77.2)	$ 44.2	$ (20.0)	$ 41.7	$ (969.9)	$ (11.3)	$ 327.9
Basic shares									157.9	162.3	166.8
Earnings per Share, Basic [Abstract]
Basic net (loss) income per share	$ (0.21)	$ (4.67)	$ (0.76)	$ (0.51)	$ (0.49)	$ 0.27	$ (0.12)	$ 0.25	$ (6.14)	$ (0.07)	$ 1.97
Earnings per Share, Diluted [Abstract]
Basic shares									157.9	162.3	166.8
Stock-based compensation (in shares)									0.0	0.0	1.6
Diluted shares									157.9	162.3	168.4
Diluted net (loss) income per share	$ (0.21)	$ (4.67)	$ (0.76)	$ (0.51)	$ (0.49)	$ 0.27	$ (0.12)	$ 0.25	$ (6.14)	$ (0.07)	$ 1.95
Antidilutive shares excluded from the computation of earnings per share (in shares)									10.0	7.8	2.4