Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Effective portion of change in fair value of foreign currency forward contracts	$ (931,000)	$ 713,000
Long-term debt and finance leases	121,305,000	121,284,000
Quoted Prices in Active Markets for Identical Assets Level (1)
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Fair value of long term debt	133,343,000	137,343,000
Foreign Currency Derivative
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Notional amount of the foreign currency derivative instruments	$ 157,076,000	$ 129,542,000
Foreign Currency Derivative | Maximum
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Maturity period of hedges	12 months
Derivatives Designated as Cash Flow Hedges
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Maturity period of hedges	3 years