Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Equity [Abstract]
Net income	$ 100.4	$ 93.2
Weighted average common shares outstanding	42.0	44.3
Incremental shares from restricted stock units, stock options and convertible debentures	0.4	1.3
Weighted average diluted shares outstanding	42.4	45.6
Basic earnings per share (in dollars per share)	$ 2.39	$ 2.10
Diluted earnings per share (in dollars per share)	$ 2.37	$ 2.04
Shares outstanding	42.1	44.1
Anti-dilutive securities excluded from diluted earnings per share (in shares)	0	0