Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements Narrative (Details)

v3.19.1
Fair Value Measurements Narrative (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2018
USD ($)
Warrant
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Aug. 31, 2018
$ / shares
shares
Jan. 12, 2018
$ / shares
shares
Oct. 21, 2016
$ / shares
shares
Class of Warrant or Right [Line Items]            
Number of warrants issued | Warrant 2          
Warrant shares (in shares) 1,239,286          
Change in fair value of warrant | $ $ 368 $ 74 $ 137      
Hale Capital, LLP            
Class of Warrant or Right [Line Items]            
Warrant shares (in shares)           314,286
Warrant, exercise price (in dollars per share) | $ / shares           $ 2.80
ESW Holdings, Inc.            
Class of Warrant or Right [Line Items]            
Warrant shares (in shares)         925,000  
Warrant, exercise price (in dollars per share) | $ / shares       $ 2.43 $ 1.96  
iStudy Co., Ltd.            
Class of Warrant or Right [Line Items]            
Warrant shares (in shares)       100,000