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, 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 a private placement, net of issuance costs |
23,319,156
|
$ 33
|
23,319,123
|
|
Issuance of shares and warrants in a 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
|
|
145,421
|
|
Proceeds from contributions to the ESPP (in shares) |
|
85,765
|
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
|
$ 1
|
|
|
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
|
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
4,557,693
|
|
|
|
Ending balance at Dec. 31, 2019 |
19,012,874
|
$ 333
|
282,153,201
|
(263,140,660)
|
Ending balance (in shares) at Dec. 31, 2019 |
|
33,203,806
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
2,321,820
|
|
2,321,820
|
|
Stock-based compensation - performance share units ("PSUs") |
(88,348)
|
|
(88,348)
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
42,827
|
|
42,827
|
|
Issuance of shares for RSUs |
|
$ 4
|
(4)
|
|
Issuance of shares for RSUs (in shares) |
|
396,559
|
|
|
Proceeds from contributions to the ESPP |
113,059
|
|
113,059
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
5,506,880
|
$ 44
|
5,506,836
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs (in shares) |
|
4,351,652
|
|
|
Net loss |
(8,597,736)
|
|
|
(8,597,736)
|
Ending balance at Mar. 31, 2020 |
18,311,376
|
$ 381
|
290,049,391
|
(271,738,396)
|
Ending balance (in shares) at Mar. 31, 2020 |
|
37,952,017
|
|
|
Beginning balance at Dec. 31, 2019 |
19,012,874
|
$ 333
|
282,153,201
|
(263,140,660)
|
Beginning balance (in shares) at Dec. 31, 2019 |
|
33,203,806
|
|
|
Net loss |
(24,359,239)
|
|
|
|
Ending balance at Sep. 30, 2020 |
19,042,028
|
$ 431
|
306,541,496
|
(287,499,899)
|
Ending balance (in shares) at Sep. 30, 2020 |
|
43,062,944
|
|
|
Beginning balance at Mar. 31, 2020 |
18,311,376
|
$ 381
|
290,049,391
|
(271,738,396)
|
Beginning balance (in shares) at Mar. 31, 2020 |
|
37,952,017
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
2,028,599
|
|
2,028,599
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
41,308
|
|
41,308
|
|
Issuance of shares for RSUs |
|
$ 2
|
(2)
|
|
Issuance of shares for RSUs (in shares) |
|
232,995
|
|
|
Proceeds from contributions to the ESPP |
104,145
|
$ 1
|
104,144
|
|
Proceeds from contributions to the ESPP (in shares) |
|
144,370
|
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
9,216,611
|
$ 33
|
9,216,578
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs (in shares) |
|
3,355,928
|
|
|
Net loss |
(8,204,666)
|
|
|
(8,204,666)
|
Ending balance at Jun. 30, 2020 |
21,497,373
|
$ 417
|
301,440,018
|
(279,943,062)
|
Ending balance (in shares) at Jun. 30, 2020 |
|
41,685,310
|
|
|
Stock-based compensation - restricted stock units ("RSUs") |
1,876,686
|
|
1,876,686
|
|
Stock-based compensation - employee stock purchase plan ("ESPP") |
96,056
|
|
96,056
|
|
Issuance of shares for RSUs |
|
$ 4
|
(4)
|
|
Issuance of shares for RSUs (in shares) |
|
361,608
|
|
|
Proceeds from contributions to the ESPP |
121,692
|
|
121,692
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs |
3,007,058
|
$ 10
|
3,007,048
|
|
Issuance of shares in an at-the-market ("ATM") offering, net of issuance costs (in shares) |
|
1,016,026
|
|
|
Net loss |
(7,556,837)
|
|
|
(7,556,837)
|
Ending balance at Sep. 30, 2020 |
$ 19,042,028
|
$ 431
|
$ 306,541,496
|
$ (287,499,899)
|
Ending balance (in shares) at Sep. 30, 2020 |
|
43,062,944
|
|
|