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Note 3 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $)
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Dec. 31, 2014
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Dec. 31, 2013
|
| Assets |
|
|
| Short-term investments |
$ 19,016,347 |
$ 13,659,812 |
| Total assets at fair value |
57,132,838 |
|
| Restricted cash – long-term |
1,325,000 |
|
| Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] |
|
|
| Assets |
|
|
| Money-market funds |
35,541,595 |
22,891,418 |
| Money Market Funds [Member] |
|
|
| Assets |
|
|
| Money-market funds |
35,541,595 |
22,891,418 |
| Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] |
|
|
| Assets |
|
|
| Total assets at fair value |
|
22,891,418 |
| Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] |
|
|
| Assets |
|
|
| Short-term investments |
20,266,243 |
13,659,812 |
| Total assets at fair value |
|
13,659,812 |
| Corporate Debt Securities [Member] |
|
|
| Assets |
|
|
| Short-term investments |
20,266,243 |
13,659,812 |
| Total assets at fair value |
|
36,551,230 |
| Fair Value, Inputs, Level 1 [Member] |
|
|
| Assets |
|
|
| Total assets at fair value |
36,866,595 |
|
| Restricted cash – long-term |
1,325,000 |
|
| Fair Value, Inputs, Level 2 [Member] |
|
|
| Assets |
|
|
| Total assets at fair value |
$ 20,266,243 |
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