Note 8 - Earnings Per Share - Calculation of Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Numerator for net income per share - basic:
Net income	$ 3,480	$ 5,453
Common Class A [Member]
Numerator for net income per share - basic:
Net income	1,738	2,722
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(12)
Net income attributable to common shareholders	1,726	2,722
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	20,792	20,742
Net income per share - basic (in dollars per share)	$ 0.08	$ 0.13
Numerator for net income per share - diluted:
Net income attributable to common shareholders for basic computation	1,726	2,722
Denominator for net income per share - diluted:
Weighted average common shares outstanding - basic (in shares)	20,792	20,742
Weighted average effect of dilutive securities – stock options (in shares)	241	392
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	21,033	21,134
Net income per share - diluted (in dollars per share)	$ 0.08	$ 0.13
Common Class B [Member]
Numerator for net income per share - basic:
Net income	1,742	2,731
Allocation of distributed and undistributed income to unvested restricted stock shareholders	(10)
Net income attributable to common shareholders	1,732	2,731
Denominator for net income per share - basic:
Weighted average common shares outstanding - basic (in shares)	3,478	3,469
Net income per share - basic (in dollars per share)	$ 0.50	$ 0.79
Numerator for net income per share - diluted:
Net income attributable to common shareholders for basic computation	$ 1,732	$ 2,731
Denominator for net income per share - diluted:
Weighted average common shares outstanding - basic (in shares)	3,478	3,469
Weighted average effect of dilutive securities – stock options (in shares)	46	72
Denominator for diluted earnings per share – adjusted weighted average shares (in shares)	3,524	3,541
Net income per share - diluted (in dollars per share)	$ 0.49	$ 0.77