Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Narrative (Details)

v3.19.1
Fair Value Measurements - Narrative (Details)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2019
USD ($)
Warrant
shares
Mar. 31, 2018
USD ($)
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 liability | $ $ (289) $ 387      
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       $ 1.96  
iStudy Co., Ltd.          
Class of Warrant or Right [Line Items]          
Warrant shares (in shares)     100,000    
Warrant, exercise price (in dollars per share) | $ / shares     $ 2.43