Derivatives and Hedging Activities - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net	$ 16.5	$ 3.8
Net losses reclassified from accumulated other comprehensive income (loss) into income	(30.6)	(11.2)	$ (19.9)
Net gains reclassified from accumulated other comprehensive income (loss) into income	15.3	20.8	38.4
Designated as hedging instruments
Derivative [Line Items]
Derivatives used in net investment hedges	4,139.8	3,149.5
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax	218.3	(235.3)
Not designated as hedging instruments | Embedded derivatives
Derivative [Line Items]
Net gain (loss) on embedded derivatives		(6.8)
Not designated as hedging instruments | Economic hedges of embedded derivatives
Derivative [Line Items]
Net gain (loss) on embedded derivatives			2.9
Not designated as hedging instruments | Foreign currency forward contracts designated as cash flow hedges
Derivative [Line Items]
Gains (losses) from foreign currency forward contracts	$ 91.2	$ (69.0)	$ 74.2