Summary of Net Gain (Loss) on Foreign Exchange Forwards Not Designated as Hedging Instruments (Detail) - Not Designated as Accounting Hedges [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) recognized in income	$ (44.9)	$ 48.3	$ (17.3)	$ 46.0
Foreign Exchange Forward [Member] | Other Nonoperating (Expense) Income [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) recognized in income	$ (44.9)	7.1	$ (17.3)	4.8
Foreign Exchange Collar [Member] | Bureau van Dijk (BvD) [Member] | Purchase Price Hedge [Member]
Derivative Instruments Gain Loss [Line Items]
Amount of gain (loss) recognized in income		$ 41.2		$ 41.2