Earnings Per Common Share - Computation of EPS (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:
Net (loss) income	$ (28.1)	$ 9.3	$ 0.8	$ (36.7)	$ (9.8)	$ 3.9	$ 4.5	$ 12.6	$ (54.7)	$ 11.2	$ 18.6
Preferred stock dividends									10.4	10.4	10.4
Net (loss) income applicable to common shareowners - basic and diluted									$ (65.1)	$ 0.8	$ 8.2
Denominator:
Weighted-average common shares outstanding - basic									205.9	197.0	196.8
Warrants									0	4.5	0.4
Stock-based compensation arrangements									0	3.2	2.8
Weighted-average common shares outstanding - diluted									205.9	204.7	200.0
Basic and diluted (loss) earnings per common share	$ (0.15)	$ 0.03	$ (0.01)	$ (0.19)	$ (0.06)	$ 0.01	$ 0.01	$ 0.05	$ (0.32)	$ 0.00	$ 0.04