Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net (loss) income	$ (13.8)	$ 2.3	$ (22.1)	$ 62.9
Preferred stock dividends	2.6	2.6	5.2	5.2
Net (loss) income applicable to common shareowners - basic and diluted	$ (16.4)	$ (0.3)	$ (27.3)	$ 57.7
Denominator:
Weighted average common shares outstanding - basic	42.4	42.2	42.4	42.1
Stock-based compensation arrangements	0.0	0.0	0.0	0.2
Weighted average common shares outstanding - diluted	42.4	42.2	42.4	42.3
Basic net (loss) earnings per common share	$ (0.39)	$ (0.01)	$ (0.64)	$ 1.37
Diluted net (loss) earnings per common share	$ (0.39)	$ (0.01)	$ (0.64)	$ 1.36
Stock Compensation Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount				0.3
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.9	0.9	0.9	0.9