|
Note 12 - Stock Options and Employee Stock Purchase Plan (Details) - Stock-based Compensation Expense (USD $)
|
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | $ 3,013,283 | $ 1,053,163 | $ 1,042,989 |
| Research and Development Expense [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | 1,604,215 | 524,495 | 511,860 |
| General and Administrative Expense [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | $ 1,409,068 | $ 528,668 | $ 531,129 |