Pension and Postretirement Benefits - Components of Net Periodic Benefit (Income) Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.2	$ 0.7
Interest cost	39.6	53.8
Expected return on plan assets	(74.1)	(75.1)
Amortization of prior service (benefit) cost	(1.3)	(1.2)
Recognized net actuarial (gain) loss	46.2	44.3
Settlement loss	158.0
Net periodic pension expense/postretirement benefit (income) expense	169.6	22.5
Pension Plans | U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.0
Interest cost	29.4	40.4
Expected return on plan assets	(51.4)	(52.3)
Amortization of prior service (benefit) cost	(0.6)	(0.6)
Recognized net actuarial (gain) loss	33.2	33.5
Settlement loss	158.0
Net periodic pension expense/postretirement benefit (income) expense	168.6	21.0
Pension Plans | International Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.2	0.7
Interest cost	10.2	13.4
Expected return on plan assets	(22.7)	(22.8)
Amortization of prior service (benefit) cost	(0.7)	(0.6)
Recognized net actuarial (gain) loss	13.0	10.8
Settlement loss	0.0
Net periodic pension expense/postretirement benefit (income) expense	1.0	1.5
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.1
Interest cost	0.4	1.1
Expected return on plan assets	(0.1)	(0.1)
Amortization of prior service (benefit) cost	(0.4)	(0.4)
Recognized net actuarial (gain) loss	(0.6)	0.3
Net periodic pension expense/postretirement benefit (income) expense	$ (0.6)	$ 1.0