Earnings (Loss) Per Unit - Basic and Diluted Earnings Per Unit (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income attributable to common unitholders	$ 170.1	$ 114.5	$ 449.2	$ 120.6
Basic and diluted partnership units:
Total weighted average basic and diluted units outstanding	429.1	467.0	430.0	467.0
Class A Common Units [Member]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income attributable to common unitholders	$ 86.3	$ 49.6	$ 227.2	$ 52.2
Basic and diluted partnership units:
Total weighted average basic and diluted units outstanding	202.0	202.0	202.0	202.0
Earnings per unit - basic and diluted:
Earnings per unit / share - basic and diluted	$ 0.43	$ 0.25	$ 1.12	$ 0.26
Partnerships Exchangeable Units [Member]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net income attributable to common unitholders	$ 83.8	$ 64.9	$ 222.0	$ 68.4
Basic and diluted partnership units:
Total weighted average basic and diluted units outstanding	227.1	265.0	228.0	265.0
Earnings per unit - basic and diluted:
Earnings per unit / share - basic and diluted	$ 0.37	$ 0.25	$ 0.97	$ 0.26