Accumulated other comprehensive loss - Schedule of Changes in Accumulated Other Comprehensive Loss by Component Net of Tax (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Jan. 01, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 1,732.8	$ 1,191.7
Impact due to adoption of ASU	[1]			$ 0.0
Other comprehensive loss before reclassifications		(105.2)	2.7
Amounts reclassified from accumulated other comprehensive loss		(5.0)	(2.8)
Net current period other comprehensive (loss) income		(110.2)	(3.3)
Ending balance		1,683.6	1,781.0
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(379.3)	(373.2)
Impact due to adoption of ASU	[1]			(3.2)
Ending balance		(489.5)	(376.5)
Cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(15.4)	8.9
Other comprehensive loss before reclassifications		(11.1)	(5.5)
Amounts reclassified from accumulated other comprehensive loss		(5.0)	(2.8)
Net current period other comprehensive (loss) income		(16.1)	(6.8)
Ending balance		(31.5)	2.1
Defined benefit pension items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(1.0)	(1.1)
Other comprehensive loss before reclassifications		0.0	0.0
Amounts reclassified from accumulated other comprehensive loss		0.0	0.0
Net current period other comprehensive (loss) income		0.0	0.0
Ending balance		(1.0)	(1.1)
Currency translation items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(362.9)	(381.0)
Other comprehensive loss before reclassifications		(94.1)	8.2
Amounts reclassified from accumulated other comprehensive loss		0.0	0.0
Net current period other comprehensive (loss) income		(94.1)	3.5
Ending balance		$ (457.0)	$ (377.5)
Accounting Standards Update 2018-02 | Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact due to adoption of ASU				(3.2)
Accounting Standards Update 2018-02 | Cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact due to adoption of ASU				1.5
Accounting Standards Update 2018-02 | Defined benefit pension items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact due to adoption of ASU				0.0
Accounting Standards Update 2018-02 | Currency translation items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Impact due to adoption of ASU				$ (4.7)

[1] Adjusted due to the adoption of ASU 2018-02 “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” on January 1, 2019.