Note 11 - Stock-based Compensation - Summary of Option Activity Under the Plans (Details) - $ / shares shares in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Outstanding, shares (in shares)	4,887
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 7.57
Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 8.06	$ 7.57
Outstanding, Weighted Average Remaining Contractual Life (Year)	6 years 40 days	5 years 295 days
Granted, shares (in shares)	1,117
Granted, Weighted Average Exercise Price (in dollars per share)	$ 10.63
Exercised, shares (in shares)	(71)
Exercised, Weighted Average Exercise Price (in dollars per share)	$ 5.79
Cancelled, shares (in shares)	(131)
Exercisable, shares (in shares)	4,017
Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 7.92
Exercisable, Weighted Average Remaining Contractual Life (Year)	4 years 295 days
Vested and expected to vest, shares (in shares)	5,392
Vested and expected to vest, Weighted Average Exercise Price (in dollars per share)	$ 8
Cancelled, Weighted Average Exercise Price (in dollars per share)	$ 8.81
Expired, shares (in shares)	(30)
Expired, Weighted Average Exercise Price (in dollars per share)	$ 26.42
Outstanding, shares (in shares)	5,772	4,887
Vested and expected to vest, Weighted Average Remaining Contractual Life (Year)	5 years 324 days