Quarterly report pursuant to Section 13 or 15(d)

Note 5 - Stockholders' Equity - Summary of Warrant Activity (Details)

v3.7.0.1
Note 5 - Stockholders' Equity - Summary of Warrant Activity (Details) - Stock Purchase Warrants [Member]
6 Months Ended
Jun. 30, 2017
$ / shares
shares
Number of warrants outstanding (in shares) | shares 2,458,543
Range One [Member]  
Upper exercise price range (in dollars per share) $ 3.90
Number of warrants outstanding (in shares) | shares 811,556
Lower exercise price range (in dollars per share) $ 3.25
Range One [Member] | Minimum [Member]  
Expiration dates May 2021 - July 2021
Range Two [Member]  
Upper exercise price range (in dollars per share) $ 6.50
Number of warrants outstanding (in shares) | shares 282,054
Lower exercise price range (in dollars per share) $ 5.80
Range Two [Member] | Minimum [Member]  
Expiration dates March 2018
Range Three [Member]  
Upper exercise price range (in dollars per share) $ 12.90
Number of warrants outstanding (in shares) | shares 39,296
Lower exercise price range (in dollars per share) $ 12.80
Range Three [Member] | Minimum [Member]  
Expiration dates January 2022
Range Four [Member]  
Upper exercise price range (in dollars per share) $ 13.30
Number of warrants outstanding (in shares) | shares 314,246
Lower exercise price range (in dollars per share) $ 13.20
Range Four [Member] | Minimum [Member]  
Expiration dates August 2017
Range Five [Member]  
Upper exercise price range (in dollars per share) $ 16.30
Number of warrants outstanding (in shares) | shares 174,544
Lower exercise price range (in dollars per share) $ 16.20
Range Five [Member] | Minimum [Member]  
Expiration dates March 2020
Range Six [Member]  
Upper exercise price range (in dollars per share) $ 19.80
Number of warrants outstanding (in shares) | shares 12,309
Lower exercise price range (in dollars per share) $ 18.60
Range Six [Member] | Minimum [Member]  
Expiration dates March 2018 - June 2018
Range Seven [Member]  
Upper exercise price range (in dollars per share) $ 27.90
Number of warrants outstanding (in shares) | shares 153,755
Lower exercise price range (in dollars per share) $ 22.10
Range Seven [Member] | Minimum [Member]  
Expiration dates March 2019 - January 2021
Range Eight [Member]  
Upper exercise price range (in dollars per share) $ 39
Number of warrants outstanding (in shares) | shares 164,114
Lower exercise price range (in dollars per share) $ 34.50
Range Eight [Member] | Minimum [Member]  
Expiration dates November 2017 - October 2019
Range Nine [Member]  
Upper exercise price range (in dollars per share) $ 39.20
Number of warrants outstanding (in shares) | shares 230,772
Lower exercise price range (in dollars per share) $ 39.10
Range Nine [Member] | Minimum [Member]  
Expiration dates October 2020 - October 2021
Range Ten [Member]  
Upper exercise price range (in dollars per share) $ 52.20
Number of warrants outstanding (in shares) | shares 275,897
Lower exercise price range (in dollars per share) $ 47.30
Range Ten [Member] | Minimum [Member]  
Expiration dates January 2019 - July 2019