Note 8 - Share-based Compensation - Employee and Director Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Granted, shares (in shares)	1,985,539,000,000	1,674,864,000,000
Options Exercisable Shares (in shares)	721,766
Options Exercisable Weighted Average Price (in dollars per share)	$ 17.14
Balance, shares (in shares)	3,761,278
Balance, weighted average exercise price (in dollars per share)	$ 9.44
Employees and Directors [Member]
Balance, shares (in shares)	1,885,383	244,046
Balance, weighted average exercise price (in dollars per share)	$ 11.46	$ 38.94
Granted, shares (in shares)	1,985,539	1,674,864
Granted, weighted average exercise price (in dollars per share)	$ 7.70	$ 7.50
Cancelled/Expired, shares (in shares)	(109,644)	(33,527)
Cancelled/Expired, weighted average exercise price (in dollars per share)	$ 14.29	$ 14.54
Options Exercisable Shares (in shares)		306,612
Options Exercisable Weighted Average Price (in dollars per share)		$ 31.49
Balance, shares (in shares)	3,761,278	1,885,383
Balance, weighted average exercise price (in dollars per share)	$ 9.44	$ 11.46