Note 2 - (Loss) Income Per Share - Calculation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net (loss) income	$ (3,189)	$ 6,071	$ 4,433	$ 11,614	$ 9,971	$ 4,417	$ 7,315	$ 26,002
Denominator:
Denominator for basic (loss) income per share – weighted-average shares (in shares)	18,458			18,343			18,426	18,337
Effect of dilutive securities:
Equivalent shares issuable upon conversion of unvested restricted shares (in shares)	261			154			194	111
Diluted weighted average shares outstanding (in shares)	18,719			18,497			18,620	18,448
Net (loss) income per share:
Basic net (loss) income per share (in dollars per share)	$ (0.17)			$ 0.63			$ 0.40	$ 1.42
Diluted net (loss) income per share (in dollars per share)	$ (0.17)			$ 0.63			$ 0.39	$ 1.41