Note 19 - Earnings Per Share - Computation of Earnings Per Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income attributable to common shares	$ 7,979,000	$ 8,337,000	$ 7,343,000	$ 7,615,000	$ 8,085,000	$ 7,845,000	$ 7,434,000	$ 8,549,000	$ 31,274,000	$ 31,913,000	$ 27,020,000
Weighted average common shares outstanding (in shares)									16,478,968	16,292,086	16,609,263
Basic earnings per common share (in dollars per share)	$ 0.48	$ 0.51	$ 0.45	$ 0.46	$ 0.49	$ 0.48	$ 0.46	$ 0.52	$ 1.90	$ 1.96	$ 1.63
Net income attributable to common shares	$ 7,979,000	$ 8,337,000	$ 7,343,000	$ 7,615,000	$ 8,085,000	$ 7,845,000	$ 7,434,000	$ 8,549,000	$ 31,274,000	$ 31,913,000	$ 27,020,000
Weighted average common shares outstanding for basic earnings per common share (in shares)									16,478,968	16,292,086	16,609,263
Add: Dilutive effects of share-based awards (in shares)									10,102	18,644	32,877
Average shares and dilutive potential common shares (in shares)									16,489,070	16,310,730	16,642,140
Diluted earnings per common share (in dollars per share)	$ 0.48	$ 0.51	$ 0.45	$ 0.46	$ 0.49	$ 0.48	$ 0.46	$ 0.52	$ 1.90	$ 1.96	$ 1.62