Note 8 - Earnings Per Share (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 shares	Jun. 30, 2014 shares	Jun. 30, 2015 shares	Jun. 30, 2014 shares
Common Class A [Member] | Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	535,383	329,427	506,565	292,182
Common Class A [Member]
Common Stock to Dividend or Distribution Payable			0.167
Common Class B [Member] | Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	56,732	17,802	50,502	10,762