Earnings Per Share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income (loss) attributable to common shareholders - basic									$ 345.6	$ 103.9	$ (398.8)
Add: Net income (loss) attributable to noncontrolling interests									336.8	133.2	(430.7)
Net income (loss) available to common shareholders and noncontrolling interests - diluted									$ 682.4	$ 237.1	$ (829.5)
Denominator:
Weighted average common shares - basic									232.9	203.5	343.7
Exchange of noncontrolling interests for common shares (Note 13)									227.8	263.5	14.5
Effect of other dilutive securities									9.3	9.0
Weighted average common shares - diluted									470.0	476.0	358.2
Basic earnings (loss) per share	$ 0.50	$ 0.37	$ 0.39	$ 0.22	$ 0.25	$ 0.25	$ 0.05	$ (0.04)	$ 1.48	$ 0.51	$ (1.16)
Diluted earnings (loss) per share	$ 0.50	$ 0.36	$ 0.38	$ 0.21	$ 0.25	$ 0.24	$ 0.05	$ (0.04)	$ 1.45	$ 0.50	$ (2.32)
Anti-dilutive securities outstanding									5.7	5.0	21.3