Earnings (Loss) 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, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net (loss) income	$ (47.1)	$ 41.2
Less: (loss) earnings and dividends allocated to participating securities	0.0	(0.4)
(Loss) earnings available for common stockholders used in calculation of basic (loss) earnings per common share	$ (47.1)	$ 40.8
Weighted average number of common shares outstanding, basic (in shares)	48.3	47.9
Basic (loss) earnings per common share (in dollars per share)	$ (0.98)	$ 0.85
Less: earnings and dividends allocated to participating securities	$ 0.0	$ (0.4)
(Loss) earnings available for common stockholders used in calculation of diluted (loss) earnings per common share	$ (47.1)	$ 40.8
Effect of shares issuable under share-based compensation plans (in shares)	0.0	0.4
Weighted average number of common shares outstanding, diluted (in shares)	48.3	48.3
Diluted (loss) earnings per common share (in dollars per share)	$ (0.98)	$ 0.85