Note 9 - Earnings Per Share - Calculation of Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Common Class A [Member]
Numerator for net income per share - basic:
Net income	$ 2,060	$ 2,272			$ 5,825	$ 7,016
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(14)				(41)
Net income attributable to common shareholders	$ 2,046	$ 2,272		$ 7,016	$ 5,784	$ 7,016
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	20,726	20,771			20,769	20,761
Net income per share – basic (in dollars per share)	$ 0.10	$ 0.11			$ 0.28	$ 0.34
Diluted Earnings Per Share:
Net income attributable to common shareholders	$ 2,046	$ 2,272		7,016	$ 5,784	$ 7,016
Denominator for net income per share - diluted:
Weighted average common shares outstanding - basic (in shares)	20,726	20,771			20,769	20,761
Weighted average effect of dilutive securities – stock options (in shares)	211	264			233	317
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	20,937	21,035			21,002	21,078
Net income per share – diluted (in dollars per share)	$ 0.10	$ 0.11			$ 0.28	$ 0.33
Common Class B [Member]
Numerator for net income per share - basic:
Net income	$ 2,078	$ 2,280			$ 5,858	$ 7,041
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(14)				(41)
Net income attributable to common shareholders	$ 2,064	$ 2,280		7,041	$ 5,817	$ 7,041
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	3,478	3,474	3,478		3,478	3,472
Net income per share – basic (in dollars per share)	$ 0.59	$ 0.66			$ 1.67	$ 2.03
Diluted Earnings Per Share:
Net income attributable to common shareholders	$ 2,064	$ 2,280		$ 7,041	$ 5,817	$ 7,041
Denominator for net income per share - diluted:
Weighted average common shares outstanding - basic (in shares)	3,478	3,474	3,478		3,478	3,472
Weighted average effect of dilutive securities – stock options (in shares)	43	62			44	66
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	3,521	3,536			3,522	3,538
Net income per share – diluted (in dollars per share)	$ 0.59	$ 0.64			$ 1.65	$ 1.99
Net income	$ 4,139	$ 4,552			$ 11,683	$ 14,057