Earnings (Loss) Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.3	0	0.3	0
Computations of basic and diluted earnings per share for income from continuing operations
Net income	$ 67.4	$ 64.3	$ 161.2	$ 136.6
Add: Loss from discontinued operations	0.1	1.5	0.8	9.3
Income from continuing operations	$ 67.5	$ 65.8	$ 162.0	$ 145.9
Weighted-average shares outstanding - basic	48.3	49.7	48.7	50.0
Effect of diluted securities attributable to stock-based payments	0.7	0.8	0.8	0.8
Weighted-average shares outstanding - diluted	49.0	50.5	49.5	50.8
Earnings per share:
Income from continuing operations, Basic	$ 1.40	$ 1.32	$ 3.33	$ 2.92
Loss from discontinued operations, Basic	$ 0.00	$ (0.03)	$ (0.02)	$ (0.19)
Net income (loss), Basic	$ 1.40	$ 1.29	$ 3.31	$ 2.73
Income from continuing operations, Diluted	$ 1.38	$ 1.30	$ 3.27	$ 2.87
Loss from discontinued operations, Diluted	$ 0.00	$ (0.03)	$ (0.01)	$ (0.18)
Net income (loss), Diluted	$ 1.38	$ 1.27	$ 3.26	$ 2.69