Quarterly report pursuant to Section 13 or 15(d)

Significant Customers And Concentrations Of Credit Risk - Additional Information (Detail)

v3.10.0.1
Significant Customers And Concentrations Of Credit Risk - Additional Information (Detail) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member] - Customer
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Concentrations Of Credit Risk And Major Customers Revenue [Line Items]        
Concentration risk percentage 44.30% 69.50% 44.10% 66.00%
Number of major customers     10