Annual report pursuant to Section 13 and 15(d)

Selected Quarterly Financial Data (Details)

v3.8.0.1
Selected Quarterly Financial Data (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
[1]
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Selected Quarterly Financial Information [Line Items]                      
Loss from operations $ (5,783) $ (5,842) $ (6,475) $ (8,149) $ (10,204) $ (9,156) $ (9,311) $ (10,581)      
Net (loss) income $ 2,812 $ (10,930) $ (4,315) $ (3,058) $ (2,472) $ (8,489) $ (5,764) $ (11,078) $ (15,174) $ (27,255) $ (43,737)
Net (loss) income per share - basic (in dollars per share) $ 0.02 $ (0.14) $ (0.03) $ (0.02) $ (0.02) $ (0.09) $ (0.06) $ (0.12)      
Net (loss) income per share - dilutive (in dollars per share) $ 0.02 $ (0.14) $ (0.03) $ (0.02) $ (0.02) $ (0.09) $ (0.10) $ (0.12)      
Weighted average common share - basic (in shares) 128,566,883 128,279,674 123,005,220 117,447,260 103,804,308 91,441,687 91,015,733 90,826,752      
Weighted average common share - dilutive (in shares) 150,847,262 128,279,674 123,005,220 117,447,260 103,804,308 91,441,687 93,930,540 90,826,752      
[1] Net Income due to gain on remeasurement of the warrant liabilities in excess of the quarter to date loss.