Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Numerator
Net income (controlling interest)	$ 128.0us-gaap_NetIncomeLoss	$ 77.2us-gaap_NetIncomeLoss
Convertible securities interest expense, net	3.8	0
Net income (controlling interest), as adjusted	$ 131.8	$ 77.2
Denominator
Average shares outstanding—basic (in shares)	54.8	53.7
Effect of dilutive instruments:
Stock options and restricted stock (in shares)	0.8	1.3
Forward equity (in shares)	0	0.2
Junior convertible securities (in shares)	2.2	0
Average shares outstanding—diluted (in shares)	57.8	55.2

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

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