Earnings (Loss) Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 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	0.1	0.3	0.1
Computations of basic and diluted earnings per share for income from continuing operations
Net income	$ 73.9	$ 64.3	$ 93.8	$ 72.3
Add: Loss from discontinued operations	0.7	0	0.7	7.8
Income from continuing operations	$ 74.6	$ 64.3	$ 94.5	$ 80.1
Weighted-average shares outstanding - basic	48.8	50.2	48.9	50.2
Effect of diluted securities attributable to stock-based payments	0.8	0.7	0.8	0.8
Weighted-average shares outstanding - diluted	49.6	50.9	49.7	51.0
Earnings per share:
Income from continuing operations, Basic	$ 1.53	$ 1.28	$ 1.93	$ 1.60
Loss from discontinued operations, Basic	$ (0.02)	$ 0.00	$ (0.01)	$ (0.16)
Net income (loss), Basic	$ 1.51	$ 1.28	$ 1.92	$ 1.44
Income from continuing operations, Diluted	$ 1.50	$ 1.26	$ 1.90	$ 1.57
Loss from discontinued operations, Diluted	$ (0.01)	$ 0.00	$ (0.01)	$ (0.15)
Net income (loss), Diluted	$ 1.49	$ 1.26	$ 1.89	$ 1.42