Condensed Statement of Changes in Stockholders' Equity - USD ($)
|
Total |
Common Stock [Member] |
Additional Paid-in Capital [Member] |
Accumulated Deficit [Member] |
Beginning balance at Dec. 31, 2017 |
$ 11,758,730
|
$ 225
|
$ 185,659,954
|
$ (173,901,449)
|
Beginning balance (in shares) at Dec. 31, 2017 |
|
22,584,588
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
4,251,961
|
|
4,251,961
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
154,545
|
|
154,545
|
|
Stock-based compensation - performance share units ("PSUs") |
202,702
|
|
202,702
|
|
Issuance of shares for RSUs |
|
$ 3
|
(3)
|
|
Issuance of shares for RSUs (in shares) |
|
341,936
|
|
|
Issuance of shares for PSUs |
|
$ 1
|
(1)
|
|
Issuance of shares for PSUs (in shares) |
|
80,098
|
|
|
Exercise of stock options |
981,053
|
$ 2
|
981,051
|
|
Exercise of stock options (in shares) |
|
179,732
|
|
|
Cashless exercise of warrants (in shares) |
|
7,989
|
|
|
Proceeds from contributions to the ESPP |
200,935
|
|
200,935
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
38,846,815
|
$ 22
|
38,846,793
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs (in shares) |
|
2,221,455
|
|
|
Net loss |
(13,443,457)
|
|
|
(13,443,457)
|
Ending balance at Mar. 31, 2018 |
42,953,284
|
$ 253
|
230,297,937
|
(187,344,906)
|
Ending balance (in shares) at Mar. 31, 2018 |
|
25,415,798
|
|
|
Beginning balance at Dec. 31, 2017 |
11,758,730
|
$ 225
|
185,659,954
|
(173,901,449)
|
Beginning balance (in shares) at Dec. 31, 2017 |
|
22,584,588
|
|
|
Net loss |
(38,387,119)
|
|
|
|
Ending balance at Sep. 30, 2018 |
26,893,028
|
$ 259
|
239,181,337
|
(212,288,568)
|
Ending balance (in shares) at Sep. 30, 2018 |
|
26,059,350
|
|
|
Beginning balance at Mar. 31, 2018 |
42,953,284
|
$ 253
|
230,297,937
|
(187,344,906)
|
Beginning balance (in shares) at Mar. 31, 2018 |
|
25,415,798
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
3,884,725
|
|
3,884,725
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
253,201
|
|
253,201
|
|
Stock-based compensation - performance share units ("PSUs") |
204,954
|
|
204,954
|
|
Issuance of shares for RSUs |
|
$ 1
|
(1)
|
|
Issuance of shares for RSUs (in shares) |
|
104,112
|
|
|
Exercise of stock options |
2,171
|
|
2,171
|
|
Exercise of stock options (in shares) |
|
872
|
|
|
Cashless exercise of warrants (in shares) |
|
11,370
|
|
|
Proceeds from contributions to the ESPP |
169,879
|
|
169,879
|
|
Proceeds from contributions to the ESPP (in shares) |
|
29,458
|
|
|
Net loss |
(12,298,371)
|
|
|
(12,298,371)
|
Ending balance at Jun. 30, 2018 |
35,169,843
|
$ 254
|
234,812,866
|
(199,643,277)
|
Ending balance (in shares) at Jun. 30, 2018 |
|
25,561,610
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
3,578,276
|
|
3,578,276
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
67,174
|
|
67,174
|
|
Stock-based compensation - performance share units ("PSUs") |
207,206
|
|
207,206
|
|
Issuance of shares for RSUs |
|
$ 3
|
(3)
|
|
Issuance of shares for RSUs (in shares) |
|
297,599
|
|
|
Exercise of stock options |
336,237
|
$ 2
|
336,235
|
|
Exercise of stock options (in shares) |
|
200,141
|
|
|
Proceeds from contributions to the ESPP |
179,583
|
|
179,583
|
|
Net loss |
(12,645,291)
|
|
|
(12,645,291)
|
Ending balance at Sep. 30, 2018 |
26,893,028
|
$ 259
|
239,181,337
|
(212,288,568)
|
Ending balance (in shares) at Sep. 30, 2018 |
|
26,059,350
|
|
|
Beginning balance at Dec. 31, 2018 |
18,370,435
|
$ 265
|
243,111,741
|
(224,741,571)
|
Beginning balance (in shares) at Dec. 31, 2018 |
|
26,526,303
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
3,083,567
|
|
3,083,567
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
87,825
|
|
87,825
|
|
Issuance of shares for RSUs |
|
$ 4
|
(4)
|
|
Issuance of shares for RSUs (in shares) |
|
434,522
|
|
|
Shares withheld for payroll tax on RSUs |
(10,207)
|
|
(10,207)
|
|
Shares withheld for payroll tax on RSUs (in shares) |
|
(1,329)
|
|
|
Shares withheld for payroll tax on performance share units ("PSUs") |
(329,159)
|
|
(329,159)
|
|
Shares withheld for payroll tax on performance share units ("PSUs") (in shares) |
|
(44,481)
|
|
|
Exercise of stock options |
400,103
|
$ 1
|
400,102
|
|
Exercise of stock options (in shares) |
|
80,201
|
|
|
Proceeds from contributions to the ESPP |
173,167
|
|
173,167
|
|
Issuance of shares and warrants in private placements, net of issuance costs |
23,319,156
|
$ 33
|
23,319,123
|
|
Issuance of shares and warrants in private placements, net of issuance costs (in shares) |
|
3,333,333
|
|
|
Net loss |
(11,019,468)
|
|
|
(11,019,468)
|
Ending balance at Mar. 31, 2019 |
34,075,419
|
$ 303
|
269,836,155
|
(235,761,039)
|
Ending balance (in shares) at Mar. 31, 2019 |
|
30,328,549
|
|
|
Beginning balance at Dec. 31, 2018 |
18,370,435
|
$ 265
|
243,111,741
|
(224,741,571)
|
Beginning balance (in shares) at Dec. 31, 2018 |
|
26,526,303
|
|
|
Net loss |
(29,007,691)
|
|
|
|
Ending balance at Sep. 30, 2019 |
21,278,035
|
$ 309
|
275,026,988
|
(253,749,262)
|
Ending balance (in shares) at Sep. 30, 2019 |
|
30,844,921
|
|
|
Beginning balance at Mar. 31, 2019 |
34,075,419
|
$ 303
|
269,836,155
|
(235,761,039)
|
Beginning balance (in shares) at Mar. 31, 2019 |
|
30,328,549
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
2,675,184
|
|
2,675,184
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
122,749
|
|
122,749
|
|
Issuance of shares for RSUs |
|
$ 2
|
(2)
|
|
Issuance of shares for RSUs (in shares) |
|
189,220
|
|
|
Proceeds from contributions to the ESPP |
145,422
|
$ 1
|
145,421
|
|
Proceeds from contributions to the ESPP (in shares) |
|
85,765
|
|
|
Net loss |
(9,803,996)
|
|
|
(9,803,996)
|
Ending balance at Jun. 30, 2019 |
27,214,778
|
$ 306
|
272,779,507
|
(245,565,035)
|
Ending balance (in shares) at Jun. 30, 2019 |
|
30,603,534
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
2,037,620
|
|
2,037,620
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
62,055
|
|
62,055
|
|
Issuance of shares for RSUs |
|
$ 3
|
(3)
|
|
Issuance of shares for RSUs (in shares) |
|
280,053
|
|
|
Shares returned (in shares) |
|
(38,666)
|
|
|
Proceeds from contributions to the ESPP |
147,809
|
|
147,809
|
|
Net loss |
(8,184,227)
|
|
|
(8,184,227)
|
Ending balance at Sep. 30, 2019 |
$ 21,278,035
|
$ 309
|
$ 275,026,988
|
$ (253,749,262)
|
Ending balance (in shares) at Sep. 30, 2019 |
|
30,844,921
|
|
|