CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Net sales	$ 348.8	$ 573.0	$ 702.1	$ 1,158.4
Cost of sales	342.8	460.4	692.6	933.1
Gross profit	6.0	112.6	9.5	225.3
Selling, general and administrative expenses	42.2	55.3	84.5	108.2
Restructuring and asset impairment charges	0.0	2.3	10.0	2.3
Goodwill impairment	52.8	0.0	52.8	0.0
Operating (loss) income	(89.0)	55.0	(137.8)	114.8
Interest expense, net	(7.9)	(5.3)	(14.6)	(10.7)
Debt extinguishment losses, net	0.0	0.0	(8.2)	0.0
Other income (expense), net	1.3	0.8	(1.1)	0.5
(Loss) income before income taxes	(95.6)	50.5	(161.7)	104.6
Income tax (benefit) expense	(10.7)	11.7	(29.7)	24.6
Net (loss) income	$ (84.9)	$ 38.8	$ (132.0)	$ 80.0
Earnings Per Share [Abstract]
Basic (in dollars per share)	$ (1.76)	$ 0.80	$ (2.74)	$ 1.65
Diluted (in dollars per share)	$ (1.76)	$ 0.79	$ (2.74)	$ 1.64
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Basic (in shares)	48.3	48.1	48.3	48.0
Diluted (in shares)	48.3	48.5	48.3	48.4