Quarterly report pursuant to Section 13 or 15(d)

Customer Concentrations - Additional Information (Detail)

v3.19.3
Customer Concentrations - Additional Information (Detail) - Customer Concentration Risk [Member] - Customer
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Revenues [Member]          
Concentration Risk [Line Items]          
Number of customers 3 1 3 1  
Concentration percentage 100.00% 99.00% 55.00% 98.00%  
Accounts Receivable [Member]          
Concentration Risk [Line Items]          
Number of customers     5   3
Concentration percentage     100.00%   86.00%