Note 1 - Significant Accounting Policies - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended											12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	[1]	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	[2]	Mar. 31, 2015	[3]	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income	$ 5,982	$ 2,869	$ 3,632	$ 4,352		$ 13,230	$ 7,627	$ 11,001		$ 10,227		$ 16,835	$ 42,085	$ 17,808
Denominator:
Denominator for basic income per share – weighted-average shares (in shares)												18,182	18,145	15,250
Effect of dilutive securities:
Equivalent shares issuable upon conversion of unvested restricted shares (in shares)												84	161	266
Equivalent shares issuable upon conversion of unvested employee stock options (in shares)													5	1
Denominator for diluted income per share adjusted weighted-average shares and assumed conversions (in shares)												18,266	18,311	15,517
Income per share:
Basic income per share (in dollars per share)	$ 0.33	$ 0.16	$ 0.20	$ 0.21		$ 0.74	$ 0.42	$ 0.60		$ 0.56		$ 0.93	$ 2.32	$ 1.17
Diluted income per share (in dollars per share)	$ 0.33	$ 0.16	$ 0.20	$ 0.21		$ 0.72	$ 0.42	$ 0.60		$ 0.56		$ 0.92	$ 2.30	$ 1.15

[1] Adjusted from 10-Q as filed due to implementation of ASU 2016-09.

[2] Includes $3.6 million in return of previously expensed insurance premiums for the commutation of our primary auto liability policy for the period of April 1, 2013, through September 30, 2014.

[3] Includes $4.7 million after tax one-time federal income tax credit.