Note 21 - Quarterly Financial Data (unaudited) (Details) - Selected Unaudited Quarterly Financial Data (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly operating data:
Interest income	$ 49,171	$ 49,177	$ 49,569	$ 49,211	$ 50,294	$ 49,851	$ 50,295	$ 50,086	$ 197,128	$ 200,526	$ 213,714
Interest expense	12,057	17,220	12,740	12,724	13,058	12,866	12,999	15,940	54,741	54,863	63,275
Net interest income	37,114	31,957	36,829	36,487	37,236	36,985	37,296	34,146	142,387	145,663	150,439
Provision (benefit) for loan losses	(3,192)	(618)	(1,092)	(1,119)	1,000	3,435	3,500	6,000	(6,021)	13,935	21,000
Other operating income	(576)	7,123	1,986	1,710	1,064	945	2,199	5,348	1,527	1,586	1,413
Other operating expense	21,685	21,437	20,624	22,093	18,894	19,050	20,213	22,419	85,839	80,576	82,326
Income before income tax expense	18,045	18,261	19,283	17,223	18,406	15,445	15,782	11,075	72,812	60,708	56,178
Income tax expense	6,988	7,060	7,598	6,927	6,458	6,024	6,155	4,319	28,573	22,956	21,847
Net income	$ 11,057	$ 11,201	$ 11,685	$ 10,296	$ 11,948	$ 9,421	$ 9,627	$ 6,756	$ 44,239	$ 37,752	$ 34,331
Basic earnings per common share (in Dollars per share)	$ 0.38	$ 0.38	$ 0.39	$ 0.34	$ 0.40	$ 0.32	$ 0.32	$ 0.22	$ 1.49	$ 1.26	$ 1.13
Diluted earnings per common share (in Dollars per share)	$ 0.38	$ 0.38	$ 0.39	$ 0.34	$ 0.40	$ 0.32	$ 0.32	$ 0.22	$ 1.48	$ 1.26	$ 1.13
Dividends per common share (in Dollars per share)	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.13	$ 0.13	$ 0.13	$ 0.13
Average common shares outstanding for:
Basic earnings per share (in Shares)	29,343	29,772	30,059	29,984	29,762	29,773	30,213	30,449	29,788	30,047	30,402
Diluted earnings per share (in Shares)	29,366	29,796	30,090	30,022	29,802	29,805	30,235	30,481	29,817	30,073	30,433