Cost-reduction actions - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Cost-reduction charges and other costs	$ 46.9	$ 13.2	$ 7.9	$ 27.5	$ 23.3	$ 0.2	$ 2.6	$ 2.6	$ 95.5	$ 28.7	$ 19.7
Charges related to work-force reductions									25.5	22.1	19.0
Other expenses related to the cost-reduction effort									70.0	6.6
Employee severance
Restructuring Cost and Reserve [Line Items]
Cost-reduction charges and other costs									39.0	25.7	27.7
Charges related to work-force reductions									39.0	25.7	27.7
Changes in estimates
Restructuring Cost and Reserve [Line Items]
Charges related to work-force reductions									(13.5)	3.6	8.7
Foreign currency losses related to exiting foreign countries
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort									32.3
Asset impairments
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort									24.0
Other expenses
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort									$ 13.7	0.9
Lease abandonment costs
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort										4.6
Asset write-offs
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort										$ 1.1
Idle leased facilities
Restructuring Cost and Reserve [Line Items]
Other expenses related to the cost-reduction effort											$ 0.7