Note 6 - Investment Securities - Investment Securities With Unrealized Losses Not Recognized In Income (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Less than 12 Months Fair Value	$ 323,654	$ 341,755
Less than 12 Months Unrealized Losses	5,658	7,036
12 Months or More Fair Value	13,108	13,429
12 Months or More Unrealized Losses	449	656
Total Fair Value	336,762	355,184
Total Unrealized Losses	6,107	7,692
US Government-sponsored Enterprises Debt Securities [Member]
Less than 12 Months Fair Value	49,292	51,657
Less than 12 Months Unrealized Losses	405	460
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	49,292	51,657
Total Unrealized Losses	405	460
US States and Political Subdivisions Debt Securities [Member]
Less than 12 Months Fair Value	73,875	91,728
Less than 12 Months Unrealized Losses	1,666	2,526
12 Months or More Fair Value	1,650	1,999
12 Months or More Unrealized Losses	8	10
Total Fair Value	75,525	93,727
Total Unrealized Losses	1,674	2,536
Residential Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	152,605	154,397
Less than 12 Months Unrealized Losses	2,078	2,485
12 Months or More Fair Value	5,522	5,841
12 Months or More Unrealized Losses	206	202
Total Fair Value	158,127	160,238
Total Unrealized Losses	2,284	2,687
Commercial Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	46,319	43,309
Less than 12 Months Unrealized Losses	1,505	1,557
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	46,319	43,309
Total Unrealized Losses	1,505	1,557
Corporate Debt Securities [Member]
Less than 12 Months Fair Value	1,563	536
Less than 12 Months Unrealized Losses	4	6
12 Months or More Fair Value	5,688	5,476
12 Months or More Unrealized Losses	231	435
Total Fair Value	7,251	6,012
Total Unrealized Losses	235	441
Mutual Funds and Equity Securities [Member]
Less than 12 Months Fair Value	0	128
Less than 12 Months Unrealized Losses	0	2
12 Months or More Fair Value	248	113
12 Months or More Unrealized Losses	4	9
Total Fair Value	248	241
Total Unrealized Losses	$ 4	$ 11