Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Net Income (Loss) Attributable to Parent	$ 78.5	$ 144.9	$ 171.7	$ 200.2
Net income		$ 144.9	$ 171.7	$ 200.2
Average common shares outstanding	43.7	45.0	44.0	44.7
Incremental shares from restricted stock units, stock options and convertible debentures	0.8	0.7	1.0	0.8
Average diluted shares outstanding	44.5	45.7	45.0	45.5
Basic earnings per share (in dollars per share)	$ 1.80	$ 3.22	$ 3.90	$ 4.48
Diluted earnings per share (in dollars per share)	$ 1.77	$ 3.17	$ 3.81	$ 4.40
Shares outstanding	43.3	45.1	43.3	45.1
Anti-dilutive securities excluded from diluted earnings per share	0	0.8	0	0.8
Number of shares of common stock issuable upon conversion of Series C debentures			1.2
Dilutive effect of the debentures (in shares)	0.3		0.4