Accumulated Other Comprehensive Loss - Details of Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ (152.3)
Other comprehensive income (loss) before reclassifications	(64.0)	$ 96.4
Less: amounts reclassified from accumulated other comprehensive loss	1.9	7.8
Other comprehensive (loss) income	(62.1)	104.2	$ (129.1)
Balance at end of period	348.6	(152.3)
Intra-entity foreign currency translation adjustment	(744.8)	(694.4)
Unrecognized Pension Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	103.4	276.7
Other comprehensive income (loss) before reclassifications	(31.5)	167.1
Less: amounts reclassified from accumulated other comprehensive loss	2.1	6.2
Other comprehensive (loss) income	(29.4)	173.3
Balance at end of period	132.8	103.4	276.7
Cumulative Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	694.4	701.9
Other comprehensive income (loss) before reclassifications	(50.4)	7.5
Less: amounts reclassified from accumulated other comprehensive loss	0.0	0.0
Other comprehensive (loss) income	(50.4)	7.5
Balance at end of period	744.8	694.4	701.9
Cumulative Translation Adjustment | Intra-entity transactions
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Intra-entity foreign currency translation adjustment	65.8	(78.2)	(8.3)
Unrecognized Gains (Losses) on Derivative Instruments | Net Investment Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	46.8	(21.0)
Other comprehensive income (loss) before reclassifications	15.0	(67.8)
Less: amounts reclassified from accumulated other comprehensive loss	0.0
Other comprehensive (loss) income	15.0	(67.8)
Balance at end of period	31.8	46.8	(21.0)
Unrecognized Gains (Losses) on Derivative Instruments | Cash Flow Hedge
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	0.3	(8.5)
Other comprehensive income (loss) before reclassifications	2.9	(10.4)
Less: amounts reclassified from accumulated other comprehensive loss	(0.2)	1.6
Other comprehensive (loss) income	2.7	(8.8)
Balance at end of period	(2.4)	0.3	(8.5)
Accumulated Other Comprehensive Loss, Net of Taxes
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	844.9	949.1
Balance at end of period	920.4	$ 844.9	$ 949.1
ASU 2018-02
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at end of period	(13.4)
Impact of Accounting Standard Update	$ (13.4)			$ (13.4)