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Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Percentage of Total Revenue or Gross Accounts Receivable Balance (Detail)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Revenue [Member] | Customer Concentration Risk [Member]          
Revenue, Major Customer [Line Items]          
Minimum percentage of revenue or gross accounts receivable balance 11.00% 13.00% 12.00% 13.00%  
Accounts Receivable [Member] | Credit Concentration Risk [Member]          
Revenue, Major Customer [Line Items]          
Minimum percentage of revenue or gross accounts receivable balance     15.00%   18.00%