Earnings Per Share (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
Earnings Per Share [Abstract]
Net income	$ 35.2	$ 64.3	$ 64.3	$ 8.0	$ 21.9	$ 29.4	$ 44.7	$ (6.1)	$ 171.8	$ 90.0	$ 88.3
Net loss from discontinued operations									8.1	45.0	23.2
Income from continuing operations									$ 179.9	$ 135.0	$ 111.5
Weighted-average shares outstanding - basic									49.8	50.7	52.5
Effect of diluted securities attributable to stock-based payments									0.8	0.7	0.9
Weighted-average shares outstanding - diluted									50.6	51.4	53.4
Earnings per share – Basic:
Income from continuing operations									$ 3.61	$ 2.66	$ 2.12
Loss from discontinued operations									$ (0.16)	$ (0.89)	$ (0.44)
Net income	$ 0.72	$ 1.29	$ 1.28	$ 0.16	$ 0.44	$ 0.58	$ 0.88	$ (0.12)	$ 3.45	$ 1.77	$ 1.68
Earnings per share – Diluted:
Income from continuing operations									$ 3.55	$ 2.63	$ 2.09
Loss from discontinued operations									$ (0.16)	$ (0.88)	$ (0.44)
Net income	$ 0.70	$ 1.27	$ 1.26	$ 0.16	$ 0.43	$ 0.57	$ 0.87	$ (0.12)	$ 3.39	$ 1.75	$ 1.65