Accumulated Other Comprehensive Income - Changes in Components of Accumulated Other Comprehensive Income, Net of Tax (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income, Beginning Balance	$ (434.0)
Accumulated Other Comprehensive Income, Ending Balance	(159.9)
Foreign Currency Translation [Member]
Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income, Beginning Balance	(323.4)
AOCI before reclassifications	367.9
Accumulated Other Comprehensive Income, Ending Balance	44.5
Unrealized (Losses) Gains on Securities [Member]
Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income, Beginning Balance	(0.1)
Accumulated Other Comprehensive Income, Ending Balance	(0.1)
Defined Benefit Plan Items [Member]
Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income, Beginning Balance	(142.8)
AOCI before reclassifications	(10.1)
Reclassifications	5.1
Accumulated Other Comprehensive Income, Ending Balance	(147.8)
Cash Flow Hedges [Member]
Other Comprehensive Income Loss [Line Items]
Accumulated Other Comprehensive Income, Beginning Balance	32.3
AOCI before reclassifications	(79.4)
Reclassifications	(9.4)
Accumulated Other Comprehensive Income, Ending Balance	$ (56.5)