CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 487.8	$ 427.4	$ 967.5	$ 816.3
Cost of sales	402.1	364.9	796.2	707.8
Gross profit	85.7	62.5	171.3	108.5
Selling, general and administrative expenses	44.9	47.1	88.8	91.7
Operating income	40.8	15.4	82.5	16.8
Interest expense	(7.3)	(7.4)	(14.5)	(14.8)
Other income, net	0.2	0.3	0.9	1.0
Income before income taxes	33.7	8.3	68.9	3.0
Income tax (benefit) expense	(58.4)	1.3	(46.6)	2.2
Net income	$ 92.1	$ 7.0	$ 115.5	$ 0.8
EARNINGS PER COMMON SHARE:
Basic (in dollars per share)	$ 1.93	$ 0.15	$ 2.43	$ 0.01
Diluted (in dollars per share)	$ 1.92	$ 0.15	$ 2.41	$ 0.01
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
Basic (in shares)	47.2	47.0	47.1	47.0
Diluted (in shares)	47.6	47.1	47.5	47.1
Cash dividends per common share (in dollars per share)	$ 0.18	$ 0.18	$ 0.36	$ 0.36