Comprehensive Income And Accumulated Other Comprehensive Income - Reclassification out of AOCI (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flow Hedges, net of tax:
Gains (loss) on cash flow hedges - Pre Tax		$ 0.1
Amount of Gain/(Loss) Reclassified from AOCI into Income, net of Tax		0.1
Pension and Other Post-Retirement Benefits, net of tax:
Amortization of actuarial losses and prior service costs included in net income - Pre Tax	$ (0.8)	(1.4)
Amortization of actuarial losses and prior service costs included in net income - Tax	0.2	0.4
Amortization of actuarial losses and prior service costs included in net income - Net of Tax	(0.6)	(1.0)
(Losses) Income Attributable to Reclassification Out Of AOCI Net Of Tax	(0.6)	(0.9)
Operating Expense [Member]
Pension and Other Post-Retirement Benefits, net of tax:
Amortization of actuarial losses and prior service costs included in net income - Pre Tax	(0.5)	(0.9)
SG&A Expense [Member]
Pension and Other Post-Retirement Benefits, net of tax:
Amortization of actuarial losses and prior service costs included in net income - Pre Tax	(0.3)	(0.5)
Currency Swap [Member] | Other Nonoperating Income (Expense) [Member]
Cash Flow Hedges, net of tax:
Gains (loss) on cash flow hedges - Pre Tax	(0.1)	$ 0.1
Interest Rate Contract [Member] | Interest Expense [Member]
Cash Flow Hedges, net of tax:
Gains (loss) on cash flow hedges - Pre Tax	$ 0.1