Note 11 - Stock Option Plans (Details) (USD $)	9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2012 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2012 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 Common Class A [Member] 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2012 Common Class A [Member] 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2013 Common Class A [Member] 2006 Employee Stock Purchase Plan [Member]	Sep. 30, 2012 Common Class A [Member] 2006 Employee Stock Purchase Plan [Member]
Note 11 - Stock Option Plans (Details) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in Dollars per share)	$ 7.36		$ 6.30
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 1,600,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 321 days
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in Shares)								1,082	848	2,846	2,471
Proceeds from Stock Options Exercised	$ 1,543,000	$ 67,000		$ 6,414	$ 4,053	$ 17,411	$ 15,266