Earnings Per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income attributable to common shareholders - basic (in usd per share)	$ 89.5	$ 90.9	$ 139.7	$ 140.9
Add: Net income attributable to noncontrolling interests (in usd per share)	86.1	88.3	134.6	138.2
Net income available to common shareholders and noncontrolling interests - diluted (in usd per share)	$ 175.6	$ 179.2	$ 274.3	$ 279.1
Denominator:
Weighted average common shares - basic (shares)	235.8	233.5	235.2	231.8
Exchange of noncontrolling interests for common shares (note 11)	226.9	227.2	226.9	228.5
Effect of other dilutive securities (shares)	15.3	9.4	15.2	8.9
Weighted average common shares - diluted (shares)	478.0	470.1	477.3	469.2
Basic earnings per share (in usd per share)	$ 0.38	$ 0.39	$ 0.59	$ 0.61
Diluted earnings per share (in usd per share)	$ 0.37	$ 0.38	$ 0.57	$ 0.59
Anti-dilutive securities outstanding (shares)	4.2	6.4	4.2	6.4