Changes in Accumulated Other Comprehensive Income/(Loss) by Component - Reconciliation of Changes in Accumulated Other Comprehensive Income/(Loss) by Component (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	$ 21.1
Beginning balance	1,996.7	$ 1,922.3	$ 1,922.3
Change in fair value of interest rate swap, net of tax		(11.7)
Reclassification of interest rate swap, net of tax	2.4
Pension liability adjustment, net of tax		(0.1)
Change in fair value of net investment hedge, net of tax		31.3
Foreign currency translation adjustment	(43.0)	(58.4)
Net current-period Other Comprehensive Income (Loss)	(40.6)	(38.9)
Accumulated Other Comprehensive Income (Loss) by Component	(19.5)		21.1
Ending balance	1,991.8	1,757.1	1,996.7
Gains and Losses on Cash Flow Hedges [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	(21.5)	(16.5)	(16.5)
Change in fair value of interest rate swap, net of tax		(11.7)
Reclassification of interest rate swap, net of tax	2.4
Net current-period Other Comprehensive Income (Loss)	2.4	(11.7)
Accumulated Other Comprehensive Income (Loss) by Component	(19.1)	(28.2)	(21.5)
Defined Benefit Pension Plans [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	(3.7)	(1.5)	(1.5)
Pension liability adjustment, net of tax		(0.1)
Net current-period Other Comprehensive Income (Loss)		(0.1)
Accumulated Other Comprehensive Income (Loss) by Component	(3.7)	(1.6)	(3.7)
Cumulative Foreign Currency Translation Adjustment [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated Other Comprehensive Income (Loss) by Component	46.3	(71.9)	(71.9)
Change in fair value of net investment hedge, net of tax		31.3
Foreign currency translation adjustment	(43.0)	(58.4)
Net current-period Other Comprehensive Income (Loss)	(43.0)	(27.1)
Accumulated Other Comprehensive Income (Loss) by Component	3.3	(99.0)	46.3
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	21.1	(89.9)	(89.9)
Ending balance	$ (19.5)	$ (128.8)	$ 21.1

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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