Note 8 - Net Income Per Share Computation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Common Class A [Member]
Numerator for net income per share - basic:
Net income	$ 2,568	$ 1,738
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(21)	(12)
Net income attributable to common shareholders	$ 2,547	$ 1,726
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	20,710	20,792
Net income per share – basic (in dollars per share)	$ 0.12	$ 0.08
Net income attributable to common shareholders	$ 2,547	$ 1,726
Weighted average effect of dilutive securities – stock options (in shares)	238	241
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	20,948	21,033
Net income per share – diluted (in dollars per share)	$ 0.12	$ 0.08
Common Class B [Member]
Numerator for net income per share - basic:
Net income	$ 2,605	$ 1,742
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(23)	(10)
Net income attributable to common shareholders	$ 2,582	$ 1,732
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	3,489	3,478
Net income per share – basic (in dollars per share)	$ 0.74	$ 0.50
Net income attributable to common shareholders	$ 2,582	$ 1,732
Weighted average effect of dilutive securities – stock options (in shares)	42	46
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	3,531	3,524
Net income per share – diluted (in dollars per share)	$ 0.73	$ 0.49
Net income	$ 5,173	$ 3,480