Quarterly report pursuant to Section 13 or 15(d)

Customer Concentrations - Additional Information (Detail)

v3.19.2
Customer Concentrations - Additional Information (Detail) - Customer Concentration Risk [Member] - Customer
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Revenues [Member]          
Concentration Risk [Line Items]          
Number of customers 2 1 3 1  
Concentration percentage 95.00% 97.00% 75.00% 97.00%  
Accounts Receivable [Member]          
Concentration Risk [Line Items]          
Number of customers     2   3
Concentration percentage     95.00%   86.00%