Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Narrative (Details)

v3.19.2
Fair Value Measurements - Narrative (Details)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
USD ($)
shares
Jun. 30, 2018
USD ($)
Jun. 30, 2019
USD ($)
Warrant
shares
Jun. 30, 2018
USD ($)
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   1,239,286        
Change in fair value of warrant liability | $ $ (1,436) $ (278) $ (1,725) $ 109      
Share price, percentage change 69.00% 118.00% 25.00% (7.00%)      
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