Note 8 - Stock Options and Stock-based Employee Compensation - Summary of Stock Option Activity (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Shares Outstanding, Beginning Balance (in shares) | shares	1,142
Weighted Average Exercise Price, Outstanding, at Beginning Period (in dollars per share) | $ / shares	$ 14.66
Weighted Average Exercise Price, Outstanding, at Ending Period (in dollars per share) | $ / shares	$ 8.36
Weighted Average Remaining Contractual Life, Outstanding (Year)	7 years 146 days
Shares Vested and Exercisable (in shares) | shares	488
Weighted Average Exercise Price, Vested and Exercisable (in dollars per share) | $ / shares	$ 26.89
Weighted Average Remaining Contractual Life, Vested and Exercisable (Year)	5 years 146 days
Vested and expected to vest (in shares) | shares	1,257
Weighted Average Exercise Price, Vested and Expected to Vest (in dollars per share) | $ / shares	$ 8.45
Shares Granted (in shares) | shares	822
Weighted Average Exercise Price, Granted (in dollars per share) | $ / shares	$ 1.23
Shares Forfeited or Expired (in shares) | shares	(53)
Weighted Average Exercise Price, Forfeited or Expired (in dollars per share) | $ / shares	$ 33.52
Shares Outstanding, Ending Balance (in shares) | shares	1,911
Weighted Average Remaining Contractual Life, Vested and Expected to Vest (Year)	8 years 109 days