Note 8 - Earnings Per Share - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Common Class A [Member]
Net income	$ 2,345	$ 2,060	$ 7,339	$ 5,825
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(21)	(14)	(64)	(41)
Net income attributable to common shareholders	$ 2,324	$ 2,046	$ 7,275	$ 5,784
Weighted average shares and share equivalents outstanding, basic (in shares)	20,716	20,726	20,712	20,769
Basic earnings per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.35	$ 0.28
Weighted average effect of dilutive securities – stock options (in shares)	352	211	305	233
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	21,068	20,937	21,017	21,002
Diluted earnings per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.35	$ 0.28
Common Class B [Member]
Net income	$ 2,384	$ 2,078	$ 7,454	$ 5,858
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(21)	(15)	(64)	(41)
Net income attributable to common shareholders	$ 2,363	$ 2,064	$ 7,390	$ 5,817
Weighted average shares and share equivalents outstanding, basic (in shares)	3,511	3,478	3,503	3,478
Basic earnings per share (in dollars per share)	$ 0.67	$ 0.59	$ 2.11	$ 1.67
Weighted average effect of dilutive securities – stock options (in shares)	45	43	54	44
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	3,556	3,521	3,557	3,522
Diluted earnings per share (in dollars per share)	$ 0.66	$ 0.59	$ 2.08	$ 1.65
Net income	$ 4,729	$ 4,139	$ 14,793	$ 11,683