Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Computations of basic and diluted earnings per share for income from continuing operations
Net income	$ 29.4	$ 33.8	$ 68.0	$ 71.6
Loss from discontinued operations	(20.3)	(1.1)	(40.5)	(11.1)
Income from continuing operations	$ 49.7	$ 34.9	$ 108.5	$ 82.7
Weighted-average shares outstanding - basic	50.6	52.2	50.8	53.0
Effect of diluted securities attributable to stock-based payments	0.7	0.6	0.7	0.9
Weighted-average shares outstanding - diluted	51.3	52.8	51.5	53.9
Earnings per share from continuing operations:
Basic	$ 0.98	$ 0.67	$ 2.13	$ 1.56
Diluted	$ 0.97	$ 0.66	$ 2.11	$ 1.53