Fair Value Measurements - Carrying Amount and Fair Values of the Company's Financial Assets and Liabilities Measured on a Recurring Basis (Detail) - Recurring [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Carrying Amount [Member]
Non-derivatives:
Cash and cash equivalents	$ 78.1	$ 90.2
Non-derivatives:
Long-term debt (including current portion)	213.6	218.4
Finance leases (including current portion)	5.2	5.9
Carrying Amount [Member] | Derivatives (Level 1 Measurement) [Member] | Foreign Currency Forward Exchange Contracts [Member]
Derivatives (Level 1 measurement):
Derivative asset	0.6	1.1
Carrying Amount [Member] | Derivatives (Level 1 Measurement) [Member] | Interest Rate Swaps [Member]
Derivatives (Level 1 measurement):
Derivative asset	2.6	1.5
Carrying Amount [Member] | Non-financial Assets and Liabilities (Level 3 Measurement) [Member]
Non-financial liabilities (Level 3 measurement):
Stock equivalent units	12.5	13.6
Fair Value [Member]
Non-derivatives:
Cash and cash equivalents	78.1	90.2
Non-derivatives:
Long-term debt (including current portion)	213.6	218.4
Finance leases (including current portion)	5.2	5.9
Fair Value [Member] | Derivatives (Level 1 Measurement) [Member] | Foreign Currency Forward Exchange Contracts [Member]
Derivatives (Level 1 measurement):
Derivative asset	0.6	1.1
Fair Value [Member] | Derivatives (Level 1 Measurement) [Member] | Interest Rate Swaps [Member]
Derivatives (Level 1 measurement):
Derivative asset	2.6	1.5
Fair Value [Member] | Non-financial Assets and Liabilities (Level 3 Measurement) [Member]
Non-financial liabilities (Level 3 measurement):
Stock equivalent units	$ 12.5	$ 13.6