Restructuring - Summary of Liabilities Recognized Related to Restructuring Plan (Detail) - 2019 Restructuring Plan [Member] $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Restructuring Cost And Reserve [Line Items]
Expenses	$ 24.6	$ 67.3
Beginning Balance		27.3
Cash payments		(40.5)
Ending Balance	54.1	54.1
Expense incurred since the start of the 2019 Restructuring Plan	103.6	103.6
Expense estimated to be recognized for the 2019 Restructuring Plan	375.0	375.0
Employee Termination Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Expenses	6.5	36.7
Beginning Balance		23.2
Cash payments		(30.8)
Ending Balance	29.1	29.1
Expense incurred since the start of the 2019 Restructuring Plan	59.9	59.9
Expense estimated to be recognized for the 2019 Restructuring Plan	155.0	155.0
Contract Termination [Member]
Restructuring Cost And Reserve [Line Items]
Expenses	4.4	9.3
Cash payments		(3.0)
Ending Balance	6.3	6.3
Expense incurred since the start of the 2019 Restructuring Plan	9.3	9.3
Expense estimated to be recognized for the 2019 Restructuring Plan	40.0	40.0
Other Restructuring [Member]
Restructuring Cost And Reserve [Line Items]
Expenses	13.7	21.3
Beginning Balance		4.1
Cash payments		(6.7)
Ending Balance	18.7	18.7
Expense incurred since the start of the 2019 Restructuring Plan	34.4	34.4
Expense estimated to be recognized for the 2019 Restructuring Plan	$ 180.0	$ 180.0