Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Stockholders' Equity - Summary of Warrant Activity (Details)

v3.10.0.1
Note 4 - Stockholders' Equity - Summary of Warrant Activity (Details) - Stock Purchase Warrants [Member]
9 Months Ended
Sep. 30, 2018
$ / shares
shares
Number of warrants outstanding (in shares) | shares 3,897,374
Range One [Member]  
Lower exercise price range (in dollars per share) $ 1.11
Upper exercise price range (in dollars per share) $ 5.79
Number of warrants outstanding (in shares) | shares 3,017,326
Range One [Member] | Minimum [Member]  
Expiration date May 31, 2021
Range One [Member] | Maximum [Member]  
Expiration date Aug. 31, 2024
Range Two [Member]  
Lower exercise price range (in dollars per share) $ 12.80
Upper exercise price range (in dollars per share) $ 12.90
Number of warrants outstanding (in shares) | shares 39,296
Expiration date Jan. 31, 2022
Range Three [Member]  
Lower exercise price range (in dollars per share) $ 16.20
Upper exercise price range (in dollars per share) $ 16.30
Number of warrants outstanding (in shares) | shares 174,544
Expiration date Mar. 31, 2020
Range Four [Member]  
Lower exercise price range (in dollars per share) $ 22.10
Upper exercise price range (in dollars per share) $ 27.90
Number of warrants outstanding (in shares) | shares 153,755
Range Four [Member] | Minimum [Member]  
Expiration date Mar. 31, 2019
Range Four [Member] | Maximum [Member]  
Expiration date Jan. 31, 2021
Range Five [Member]  
Lower exercise price range (in dollars per share) $ 34.50
Upper exercise price range (in dollars per share) $ 39
Number of warrants outstanding (in shares) | shares 5,784
Expiration date Oct. 31, 2019
Range Six [Member]  
Lower exercise price range (in dollars per share) $ 39.10
Upper exercise price range (in dollars per share) $ 39.20
Number of warrants outstanding (in shares) | shares 230,772
Range Six [Member] | Minimum [Member]  
Expiration date Oct. 31, 2020
Range Six [Member] | Maximum [Member]  
Expiration date Oct. 31, 2021
Range Seven [Member]  
Lower exercise price range (in dollars per share) $ 47.30
Upper exercise price range (in dollars per share) $ 52.20
Number of warrants outstanding (in shares) | shares 275,897
Range Seven [Member] | Minimum [Member]  
Expiration date Jan. 31, 2019
Range Seven [Member] | Maximum [Member]  
Expiration date Jul. 31, 2019