Earnings per Common Share - Schedule of Calculations of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income (loss)	$ 23.4	$ (6.2)
Less: earnings and dividends allocated to participating securities	(0.2)	0.0
Earnings (loss) available for common stockholders used in calculation of basic earnings (loss) per common share	$ 23.2	$ (6.2)
Weighted average number of common shares outstanding, basic (in shares)	47.1	46.9
Basic earnings per common share (in dollars per share)	$ 0.49	$ (0.13)
Earnings (loss) available for common stockholders used in calculation of diluted earnings (loss) per common share	$ 23.2	$ (6.2)
Effect of shares issuable under share-based compensation plans (in shares)	0.2	0.0
Weighted average number of common shares outstanding, diluted (in shares)	47.3	46.9
Diluted earnings per common share (in dollars per share)	$ 0.49	$ (0.13)