CONDENSED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands  | 
6 Months Ended | |
|---|---|---|
Jun. 30, 2017  | 
Jun. 30, 2016  | 
|
| Proceeds from issuance of common stock and warrants, offering cost | $ 5,671 | $ 0 | 
| X | ||||||||||
- Definition The cash outflow for cost incurred directly with the issuance of an equity security. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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