Note 5 - Stockholders' Equity - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Options Outstanding (in shares)	1,691,987
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 22.60
Weighted- average remaining contractual life (Year)	4 years 255 days	5 years 36 days
Options Granted (in shares)	246,982
Options Granted, Weighted Average Exercise Price (in dollars per share)	$ 1.92
Options Exercised (in shares)
Options Forfeited/Expired (in shares)	(44,892)
Options Forfeited/Expired, Weighted Average Exercise Price (in dollars per share)	$ 28.67
Options Outstanding (in shares)	1,894,077	1,691,987
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 19.76	$ 22.60
Aggregate intrinsic value	$ 108,000
Options Exercisable (in shares)	1,576,364
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 22.92
Options Exercisable, Weighted Average Remaining Contractual Life (Year)	3 years 292 days
Options Exercisable, Aggregate Intrinsic Value