Quarterly report pursuant to Section 13 or 15(d)

Presentation and Summary of Significant Accounting Policies - Additional Information (Details)

v3.19.3
Presentation and Summary of Significant Accounting Policies - Additional Information (Details)
$ in Thousands
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
Sep. 30, 2019
USD ($)
Customer
Sep. 30, 2018
USD ($)
Customer
Sep. 30, 2019
USD ($)
Customer
Sep. 30, 2018
USD ($)
Customer
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Significant Accounting Policies [Line Items]              
Negative cash flows from operations       $ 18,428 $ 24,967 $ 42,227 $ 31,911
Net loss   $ 14,197 $ 15,941 47,194 43,319 61,104 $ 59,601
Accumulated deficit   217,605   217,605   170,411  
Proceeds from common stock offerings, net $ 32,780     17,302 $ 32,782    
Cash and cash equivalents   $ 49,188   $ 49,188   $ 37,539  
Sales Revenue, Net [Member] | Customer Concentration Risk [Member]              
Significant Accounting Policies [Line Items]              
Number of major customers | Customer   10 10 10 10    
Concentration risk percentage   30.10% 44.30% 23.40% 44.10%    
Equity Distribution Agreement [Member]              
Significant Accounting Policies [Line Items]              
Proceeds from common stock offerings, net       $ 17,531      
Equity Distribution Agreement [Member] | Maximum [Member]              
Significant Accounting Policies [Line Items]              
Aggregate available offering price, common stock       $ 27,679