EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net (loss) income	$ (77.2)	$ 44.2	$ (20.0)	$ 41.7	$ 53.3	$ 195.1	$ 58.6	$ 20.9	$ (11.3)	$ 327.9	$ 549.5
Basic shares (in shares)									162.3	166.8	166.2
Earnings per Share, Basic [Abstract]
Basic net (loss) income per share (in dollars per share)	$ (0.49)	$ 0.27	$ (0.12)	$ 0.25	$ 0.32	$ 1.17	$ 0.35	$ 0.13	$ (0.07)	$ 1.97	$ 3.31
Earnings per Share, Diluted [Abstract]
Basic shares (in shares)									162.3	166.8	166.2
Stock-based compensation (in shares)									0.0	1.6	2.3
Diluted shares (in shares)									162.3	168.4	168.5
Diluted net (loss) income per share (in dollars per share)	$ (0.49)	$ 0.27	$ (0.12)	$ 0.25	$ 0.32	$ 1.16	$ 0.35	$ 0.12	$ (0.07)	$ 1.95	$ 3.26
Antidilutive shares excluded from the computation of earnings per share (in shares)									7.8	2.4	1.6