Earnings per Common Share - Schedule of Calculations of Basic and Diluted Earnings from Continuing Operations per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income	$ (118.4)	$ 39.9	$ 38.8	$ 41.2	$ 48.9	$ 51.1	$ 35.5	$ 31.5	$ 1.5	$ 167.0	$ 188.5
Less: earnings and dividends allocated to participating securities									(0.4)	(1.9)	(1.7)
Earnings available for common shareholders used in calculation of basic earnings per share									$ 1.1	$ 165.1	$ 186.8
Weighted average number of common shares outstanding, basic (in shares)	48.1	48.1	48.1	47.9	47.7	47.7	47.7	47.6	48.1	47.7	47.2
Basic earnings per common share (in dollars per share)	$ (2.46)	$ 0.82	$ 0.80	$ 0.85	$ 1.01	$ 1.06	$ 0.73	$ 0.66	$ 0.02	$ 3.46	$ 3.96
Earnings available for common shareholders used in calculation of diluted earnings per share									$ 1.1	$ 165.1	$ 186.8
Effect of shares issuable under share-based compensation plans (in shares)									0.1	0.4	0.4
Weighted average number of common shares outstanding, diluted (in shares)	48.1	48.3	48.5	48.3	48.1	48.1	48.0	48.2	48.2	48.1	47.6
Diluted earnings per common share (in dollars per share)	$ (2.46)	$ 0.82	$ 0.79	$ 0.85	$ 1.00	$ 1.05	$ 0.73	$ 0.65	$ 0.02	$ 3.43	$ 3.92