Note 12 - Earnings (Loss) Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income (loss)		$ 3,394		$ 6,211		$ 10,203		$ 5,266		$ (2,600)		$ (6,236)		$ (3,488)		$ (3,093)		$ 25,074	$ (15,417)	$ (7,515)
Weighted average shares used to compute basic EPS (in shares)																		40,039	37,578
Dilutive effect of share-based awards (in shares)	[1]																	224
Weighted average shares used to compute diluted EPS (in shares)																		40,263	37,578
Basic (in dollars per share)		$ 0.08	[2]	$ 0.15	[2]	$ 0.25	[2]	$ 0.13	[2]	$ (0.07)	[2]	$ (0.16)	[2]	$ (0.09)	[2]	$ (0.10)	[2]	$ 0.63	$ (0.41)
Diluted (in dollars per share)		$ 0.08	[2]	$ 0.15	[2]	$ 0.25	[2]	$ 0.13	[2]	$ (0.07)	[2]	$ (0.16)	[2]	$ (0.09)	[2]	$ (0.10)	[2]	$ 0.62	$ (0.41)

[1] The 2017 period excludes the shares issuable under outstanding option awards as their effect would have been antidilutive.

[2] The sum of quarterly per share amounts may not equal amounts reported for the annual periods due to the effects of rounding.