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
Net Income
Net Income, Basic									$ 82.7	$ 109.0	$ 231.0
Net Income, Diluted									$ 82.7	$ 109.0	$ 231.0
Weighted Average Common Shares
Basic (in shares)									42.8	42.7	42.9
Effect of Dilutive Securities (in shares)									0.5	0.3	0.3
Diluted (in shares)									43.3	43.0	43.2
Per Common Share Amount
Net income, Basic (in dollars per share)	$ 0.36	$ 0.84	$ 0.43	$ 0.29	$ 0.48	$ 0.97	$ 0.76	$ 0.33	$ 1.93	$ 2.55	$ 5.38
Effect of Dilutive Securities (in dollars per shares)									(0.02)	(0.02)	(0.03)
Net income, Diluted (in dollars per share)	$ 0.36	$ 0.84	$ 0.43	$ 0.29	$ 0.48	$ 0.97	$ 0.76	$ 0.33	$ 1.91	$ 2.53	$ 5.35