Earnings (Loss) per Common Share (Summary of Calculations of Earnings (Loss) per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net earnings (loss)	$ 306.6	$ (234.3)	$ 46.3
Participating warrants dividend	0.0	(2.8)	(3.6)
Series A preferred stock dividend	0.0	(56.5)	(55.9)
Accretion of Series A preferred stock	0.0	(18.2)	(17.6)
Loss on redemption of Series A preferred stock	0.0	(163.6)	0.0
Other securities dividends	0.0	(0.6)	(1.2)
Undistributed earnings allocated to participating securities	(15.2)	0.0	0.0
Basic earnings (loss) attributable to common shareholders	$ 291.4	$ (476.0)	$ (32.0)
Basic weighted average common shares outstanding (in shares)	46.2	45.7	45.3
Basic earnings (loss) per common share (in dollars per share)	$ 6.31	$ (10.41)	$ (0.71)
Basic weighted average common shares outstanding (in shares)	46.2	45.7	45.3
Dilutive effect of stock options and equivalents (in shares)	0.3	0.0	0.2
Diluted weighted average common shares outstanding (in shares)	46.5	45.7	45.5
Diluted earnings (loss) attributable to common shareholders	$ 291.4	$ (476.0)	$ (32.0)
Diluted earnings (loss) per common share (in dollars per share)	$ 6.27	$ (10.41)	$ (0.70)