EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Numerator:
Net earnings	$ 32.3	$ (2.1)	$ 1.7	$ 27.6	$ 56.1	$ 10.6	$ (11.8)	$ 7.6	$ 59.5	$ 62.5	$ 68.8
Less: net earnings allocated to participating securities									(1.3)	(1.1)	(0.5)
Net earnings available to common stockholders									$ 58.2	$ 61.4	$ 68.3
Denominator:
Weighted average common shares outstanding, shares for basic earnings per share (in shares)	33,958	33,947	33,915	33,892	33,886	33,884	33,883	33,874	33,928	33,882	33,848
Weighted average equity awards outstanding (in shares)									0	0	0
Shares for diluted earnings per share (in shares)	33,977	33,947	33,915	33,892	33,886	33,884	33,883	33,874	33,928	33,882	33,848
Net earnings per common share, basic (in dollars per share)	$ 0.94	$ (0.07)	$ 0.04	$ 0.80	$ 1.64	$ 0.31	$ (0.36)	$ 0.22	$ 1.72	$ 1.82	$ 2.02
Net earnings per common share, diluted (in dollars per share)	$ 0.94	$ (0.07)	$ 0.04	$ 0.80	$ 1.63	$ 0.31	$ (0.36)	$ 0.22	$ 1.72	$ 1.81	$ 2.02
Net earnings allocated to participating securities (in shares)									397	307	186
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive weighted options outstanding (in shares)									1,188	1,067	788