Note 9 - Stock Options and Stock-based Employee Compensation - Summary of Stock Option Activity (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Shares Outstanding, Beginning Balance (in shares) | shares	4,417
Weighted Average Exercise Price, Outstanding, at Beginning Period (in dollars per share) | $ / shares	$ 6.73
Shares Granted (in shares) | shares	824
Weighted Average Exercise Price, Granted (in dollars per share) | $ / shares	$ 4.11
Shares Forfeited or Expired (in shares) | shares	(4)
Weighted Average Exercise Price, Forfeited or Expired (in dollars per share) | $ / shares	$ 576.33
Shares Outstanding, Ending Balance (in shares) | shares	5,237
Weighted Average Exercise Price, Outstanding, at Ending Period (in dollars per share) | $ / shares	$ 5.91
Weighted Average Remaining Contractual Life, Outstanding (Year)	9 years 255 days
Shares Vested and Exercisable (in shares) | shares	69
Weighted Average Exercise Price, Vested and Exercisable (in dollars per share) | $ / shares	$ 130.39
Weighted Average Remaining Contractual Life, Vested and Exercisable (Year)	6 years 255 days
Vested and expected to vest (in shares) | shares	4,942
Weighted Average Exercise Price, Vested and Expected to Vest (in dollars per share) | $ / shares	$ 5.89
Weighted Average Remaining Contractual Life, Vested and Expected to Vest (Year)	9 years 255 days