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		9 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Net loss	$ (7.5)	$ (40.5)	$ (51.7)	$ (172.5)
Dividends allocated to participating securities	0.0	(0.1)	(0.1)	(0.3)
Loss available for common stockholders used in calculation of basic loss per common share	$ (7.5)	$ (40.6)	$ (51.8)	$ (172.8)
Weighted average number of common shares outstanding, basic (in shares)	48.6	48.3	48.5	48.3
Basic loss per common share (in dollars per share)	$ (0.16)	$ (0.84)	$ (1.07)	$ (3.58)
Dividends allocated to participating securities	$ 0.0	$ (0.1)	$ (0.1)	$ (0.3)
Loss available for common stockholders used in calculation of diluted loss per common share	$ (7.5)	$ (40.6)	$ (51.8)	$ (172.8)
Effect of shares issuable under share-based compensation plans (in shares)	0.0	0.0	0.0	0.0
Weighted average number of common shares outstanding, diluted (in shares)	48.6	48.3	48.5	48.3
Diluted loss per common share (in dollars per share)	$ (0.16)	$ (0.84)	$ (1.07)	$ (3.58)