Annual report pursuant to Section 13 and 15(d)

Basis of Presentation - Additional Information (Detail)

v3.19.1
Basis of Presentation - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 25, 2019
Jul. 17, 2018
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2013
Dec. 31, 2012
Organization Consolidation And Presentation Of Financial Statements [Line Items]                              
Net loss     $ 2,755,620 $ 2,757,835 $ 2,281,289 $ 2,119,397 $ 1,460,733 $ 2,067,230 $ 1,220,866 $ 1,982,696 $ 9,914,141 $ 6,731,525      
Cash used in operations                     9,079,817 6,363,853      
Accumulated deficit     $ (111,373,608)       $ (101,400,797)       (111,373,608) (101,400,797)      
Gross proceeds from issuance of preferred and common stock, exercise of warrants and conversion of a note payable to shareholder and accrued expenses to preferred stock                     25,105,500 $ 9,684,799 $ 4,666,667 $ 14,900,000 $ 13,000,000
Proceeds from public offering   $ 13,800,000                 $ 13,800,000        
Underwritten Public Offering [Member] | Subsequent Event [Member]                              
Organization Consolidation And Presentation Of Financial Statements [Line Items]                              
Proceeds from public offering $ 12,500,000