Quarterly report pursuant to Section 13 or 15(d)

Nature of Business (Details)

v3.19.1
Nature of Business (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Apr. 09, 2019
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Class Of Stock [Line Items]            
Net Loss   $ 16,461 $ 14,463 $ 62,300 $ 54,000 $ 47,700
Accumulated deficit   (234,006)   $ (217,545)    
Cash equivalents and marketable securities   $ 75,900        
Subsequent Event            
Class Of Stock [Line Items]            
Gross proceeds from public offerings $ 70,000