Quarterly report pursuant to Section 13 or 15(d)

Customer Concentration - Additional Information (Detail)

v3.19.1
Customer Concentration - Additional Information (Detail) - Customer Concentration Risk [Member] - Customer
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Revenues [Member]      
Concentration Risk [Line Items]      
Number of customers 4 1  
Concentration percentage 98.00% 100.00%  
Accounts Receivable [Member]      
Concentration Risk [Line Items]      
Number of customers 4   3
Concentration percentage 98.00%   86.00%