Accumulated Other Comprehensive Loss - After-Tax Components of and Changes in Accumulated Other Comprehensive (Loss) Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 2,363.0	$ 2,453.8	$ 2,263.1
Amounts reclassified from accumulated other comprehensive (loss) income into earnings	(4.4)	(3.8)
Other comprehensive income (loss), net of tax	32.7	(19.4)	(45.8)
Ending Balance	2,601.1	2,363.0	2,453.8
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(28.0)	(13.3)	31.0
Amounts classified into accumulated other comprehensive (loss) income	33.8	(14.7)	(44.3)
Other comprehensive income (loss), net of tax	33.8	(14.7)	(44.3)
Ending Balance	5.8	(28.0)	(13.3)
Derivative Hedging Losses (Gains) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(0.6)	2.1	(0.6)
Amounts classified into accumulated other comprehensive (loss) income	(1.0)	(6.2)	4.5
Amounts reclassified from accumulated other comprehensive (loss) income into earnings	(0.8)	3.5	(1.8)
Other comprehensive income (loss), net of tax	(1.8)	(2.7)	2.7
Ending Balance	(2.4)	(0.6)	2.1
Defined benefit plan items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(43.3)	(41.3)	(37.1)
Amounts classified into accumulated other comprehensive (loss) income	4.3	5.3	(1.4)
Amounts reclassified from accumulated other comprehensive (loss) income into earnings	(3.6)	(7.3)	(2.8)
Other comprehensive income (loss), net of tax	0.7	(2.0)	(4.2)
Ending Balance	(42.6)	(43.3)	(41.3)
Accumulated Other Comprehensive (Loss) Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(71.9)	(52.5)	(6.7)
Amounts classified into accumulated other comprehensive (loss) income	37.1	(15.6)	(41.2)
Amounts reclassified from accumulated other comprehensive (loss) income into earnings	(4.4)	(3.8)	(4.6)
Other comprehensive income (loss), net of tax	32.7	(19.4)	(45.8)
Ending Balance	$ (39.2)	$ (71.9)	$ (52.5)