Annual report pursuant to Section 13 and 15(d)

STOCK-BASED COMPENSATION - Employee Stock Purchase Plan (Details)

v3.10.0.1
STOCK-BASED COMPENSATION - Employee Stock Purchase Plan (Details)
 12 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
item
shares
Dec. 31, 2017
$ / shares
shares
Dec. 31, 2016
$ / shares
shares
Jun. 30, 2018
USD ($)
Stock Based Compensation        
Total incremental fair value for the Purchase Plan reset | $ $ 879,000     $ 1,000,000
Purchase Plan        
Stock Based Compensation        
Purchase price expressed as a percentage of fair market value of common stock on the first day of the offering period 85.00%      
Purchase price expressed as a percentage of fair market value of common stock on the purchase date 85.00%      
Number of shares of common stock issued | shares 783,984 403,302 482,746  
Average price of shares issued (in dollars per share) | $ / shares 1.92 1.87 1.89  
Weighted average fair value of stock purchased (in dollars per share) | $ / shares $ 1.27 $ 0.99 $ 0.98  
Number of shares of common stock available for future issuance | shares 1,331,584      
Award offering period 24 months      
Number of purchase periods per award offering period | item 4      
Award purchase period 6 months