Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net (loss) income	$ (8.3)	$ 60.6
Preferred stock dividends	2.6	2.6
Net (loss) income applicable to common shareowners - basic and diluted	$ (10.9)	$ 58.0
Denominator:
Weighted average common shares outstanding - basic	42.3	42.1
Stock-based compensation arrangements	0.0	0.2
Weighted average common shares outstanding - diluted	42.3	42.3
Basic net (loss) earnings per common share	$ (0.26)	$ 1.38
Diluted net (loss) earnings per common share	$ (0.26)	$ 1.37
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		0.2
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