Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net (loss) income	$ (11.2)	$ 18.8	$ 51.3	$ 103.4
Preferred stock dividends	2.6	2.6	7.8	7.8
Net (loss) income applicable to common shareowners - basic and diluted	$ (13.8)	$ 16.2	$ 43.5	$ 95.6
Denominator:
Weighted average common shares outstanding - basic	42.2	42.0	42.1	42.0
Stock-based compensation arrangements	0.0	0.1	0.2	0.1
Weighted average common shares outstanding - diluted	42.2	42.1	42.3	42.1
Basic (loss) earnings per common share	$ (0.33)	$ 0.39	$ 1.03	$ 2.28
Diluted (loss) earnings per common share	$ (0.33)	$ 0.38	$ 1.03	$ 2.27
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	0.2	0.4
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