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Concentration of Risks - Additional Information (Detail) - Customer
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Customer Concentration Risk | Total revenue          
Concentration Risk [Line Items]          
Number of customer that individually represented more than 10% of total revenue and accounts receivable 1 1 1 0  
Concentration risk percentage 11.00% 11.00% 13.00%    
Credit Concentration Risk | Total accounts receivable          
Concentration Risk [Line Items]          
Number of customer that individually represented more than 10% of total revenue and accounts receivable     1   0
Concentration risk percentage     11.00%