Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income, basic EPS	$ 5.5	$ 2.4
Weighted-Average Shares Outstanding, basic EPS	23.2	23.0
Net Income Per Common Share, basic EPS (in dollars per share)	$ 0.24	$ 0.11
Effect of dilutive common share equivalents: [Abstract]
Net Income, diluted EPS	$ 5.5	$ 2.4
Weighted-Average Shares Outstanding, diluted EPS	23.3	23.2
Net Income Per Common Share, diluted EPS (in dollars per share)	$ 0.24	$ 0.10
Restricted Stock Units
Effect of dilutive common share equivalents: [Abstract]
Incremental common shares attributable to share-based payment arrangements, restricted stock units	0.1	0.2
Net income per common share, share-based payment arrangements (in dollars per share)	$ 0.00	$ (0.01)