Restructuring - Summary of Liabilities Recognized Related to Restructuring Plan (Detail) - 2019 Restructuring Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Beginning Balance	$ 27.3
Additions	108.2	$ 36.3
Cash payments	(72.2)	(9.0)
Ending Balance	64.7	27.3
Foreign currency exchange rate changes	1.4
Expense incurred since the start of the 2019 Restructuring Plan	144.5
Pre-tax restructuring charges	375.0
Employee Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance	23.2
Additions	55.3	23.2
Cash payments	(41.2)
Ending Balance	38.7	23.2
Foreign currency exchange rate changes	1.4
Expense incurred since the start of the 2019 Restructuring Plan	78.5
Pre-tax restructuring charges	200.0
Contract Termination [Member]
Restructuring Cost And Reserve [Line Items]
Additions	15.8
Cash payments	(4.9)
Ending Balance	10.9
Expense incurred since the start of the 2019 Restructuring Plan	15.8
Pre-tax restructuring charges	25.0
Other Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Beginning Balance	4.1
Additions	37.1	13.1
Cash payments	(26.1)	(9.0)
Ending Balance	15.1	$ 4.1
Expense incurred since the start of the 2019 Restructuring Plan	50.2
Pre-tax restructuring charges	$ 150.0