Retirement Plans - Amounts Recognized in Other Comprehensive Loss (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of Net actuarial loss (gain)	$ 7.9
Amortization of Net prior service credit	0.0
Amounts arising during the period, Net actuarial loss	(17.7)
Amounts arising during the period, Net prior service cost	(0.7)
Amounts arising during the period, Settlements	1.9
Amounts arising during the period, Foreign currency gain (loss)	0.1
Amounts arising during the period, Other	0.0
Total	(8.5)
OPEB
Defined Benefit Plan Disclosure [Line Items]
Amortization of Net actuarial loss (gain)	(0.6)
Amortization of Net prior service credit	(3.3)
Amounts arising during the period, Net actuarial loss	(1.8)
Amounts arising during the period, Net prior service cost	30.7
Amounts arising during the period, Settlements	0.0
Amounts arising during the period, Foreign currency gain (loss)	(2.0)
Amounts arising during the period, Other	0.8
Total	$ 23.8