Pension and Other Postretirement Benefit Plans - Amounts Recorded in Accumulated Other Comprehensive Loss Not Yet Recognized in Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Pension | U.S.
Defined Benefit Plan Disclosure [Line Items]
Net unrecognized actuarial gain (loss)	$ (105.9)	$ (86.1)
Prior service (cost) credit	0.0	0.0
Pretax amounts recorded in accumulated other comprehensive loss not yet recognized in net periodic benefit cost (credit)	(105.9)	(86.1)
Pension | Foreign
Defined Benefit Plan Disclosure [Line Items]
Net unrecognized actuarial gain (loss)	(135.9)	(106.8)
Prior service (cost) credit	(1.2)	(0.6)
Pretax amounts recorded in accumulated other comprehensive loss not yet recognized in net periodic benefit cost (credit)	(137.1)	(107.4)
Other Postretirement | U.S.
Defined Benefit Plan Disclosure [Line Items]
Net unrecognized actuarial gain (loss)	19.6	26.6
Prior service (cost) credit	1.9	1.9
Pretax amounts recorded in accumulated other comprehensive loss not yet recognized in net periodic benefit cost (credit)	21.5	28.5
Other Postretirement | Foreign
Defined Benefit Plan Disclosure [Line Items]
Net unrecognized actuarial gain (loss)	(0.9)	(0.9)
Prior service (cost) credit	0.1	0.3
Pretax amounts recorded in accumulated other comprehensive loss not yet recognized in net periodic benefit cost (credit)	$ (0.8)	$ (0.6)