Other Current Liabilities - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Other Current Liabilities [Line Items]
Pre-tax restructuring expense		$ 3.0
Restructuring expense incurred		2.0
Severance charges		1.5
Inventory write-down charges		0.4
Payments for planned restructuring		0.1
Accrued in other current liabilities related to restructuring		$ 1.5
Scenario, Forecast [Member]
Other Current Liabilities [Line Items]
Pre-tax restructuring expense	$ 3.0