Annual report pursuant to Section 13 and 15(d)

Stock-based Compensation - Option Valuation Method - Additional Information (Details)

v3.19.1
Stock-based Compensation - Option Valuation Method - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]    
Weighted average value of options granted in period (in dollars per share) $ 0.90 $ 1.39
Aggregate fair value of options granted $ 1.1 $ 1.8