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Trade Receivables, Net - Additional Information (Detail) - Customers
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Disclosure of financial assets [Line Items]    
Number of largest customers 5 5
Percentage of accounts receivable from largest customers 33.00% 30.00%
Bottom of range [member]    
Disclosure of financial assets [Line Items]    
Average credit terms 30 days  
Top of range [member]    
Disclosure of financial assets [Line Items]    
Average credit terms 90 days