Earnings (Loss) Per Common Share - Computation of Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net earnings	$ 37.8	$ 6.1	$ 18.6	$ 17.0	$ 43.9	$ 35.6
Participating warrants dividend	(0.9)		(0.9)		(1.9)	(1.8)
Preferred stock dividend	(14.1)		(14.4)		(28.5)	(28.4)
Accretion of redeemable, convertible Series A preferred stock	(4.5)		(4.3)		(9.0)	(8.6)
Other securities dividends	(0.3)		(0.6)		(0.3)	(1.0)
Earnings (loss) attributable to common shareholders	$ 18.0		$ (1.6)		$ 4.2	$ (4.2)
Weighted average common shares outstanding (in shares)	45.7		45.3		45.7	45.2
Basic earnings (loss) per common share (in usd per share)	$ 0.39		$ (0.03)		$ 0.09	$ (0.09)
Dilutive effect of stock options and equivalents (in shares)	0.0		0.4		0.0	0.5
Dilutive effect of participating warrants (in shares)	1.6		1.6		0.0	1.6
Diluted average shares outstanding (in shares)	47.3		47.3		45.7	47.3
Diluted earnings (loss) attributable to common shareholders	$ 19.0		$ (0.5)		$ 4.2	$ (2.1)
Diluted earnings (loss) per common share (in usd per share)	$ 0.40		$ (0.01)		$ 0.09	$ (0.05)