Note 18 - Earnings Per Share - Computation of Earnings Per Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income attributable to common shares	$ 14,082,000	$ 10,686,000	$ 8,697,000	$ 10,673,000	$ 13,317,000	$ 12,600,000	$ 11,715,000	$ 11,824,000	$ 44,138,000	$ 49,456,000	$ 42,024,000
Weighted average common shares outstanding (in shares)									16,268,689	16,405,159	16,600,612
Basic earnings per common share (in dollars per share)	$ 0.86	$ 0.66	$ 0.54	$ 0.65	$ 0.81	$ 0.77	$ 0.71	$ 0.72	$ 2.71	$ 3.01	$ 2.53
Net income	$ 14,082,000	$ 10,686,000	$ 8,697,000	$ 10,673,000	$ 13,317,000	$ 12,600,000	$ 11,715,000	$ 11,824,000	$ 44,138,000	$ 49,456,000	$ 42,024,000
Weighted average common shares outstanding for basic earnings per common share (in shares)									16,268,689	16,405,159	16,600,612
Add: Dilutive effects of share-based awards (in shares)									630	3,976	5,804
Average shares and dilutive potential common shares (in shares)									16,269,319	16,409,135	16,606,416
Diluted earnings per common share (in dollars per share)	$ 0.86	$ 0.66	$ 0.54	$ 0.65	$ 0.81	$ 0.77	$ 0.71	$ 0.72	$ 2.71	$ 3.01	$ 2.53