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Financial Instruments - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Fair Value Of Financial Instruments [Line Items]    
Fair value of note payable $ 5,300 $ 5,300
Cash and cash equivalents 33,089 29,902
Cash held outside United States, principally in Netherlands, United Kingdom, China, and Canada 21,800 19,700
Credit Facility [Member]    
Fair Value Of Financial Instruments [Line Items]    
Fair value of debt issued $ 87,200 $ 114,900