Note 6 - Investment Securities - Investment Securities With Unrealized Losses Not Recognized In Income (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Less than 12 Months Fair Value	$ 302,422	$ 341,755
Less than 12 Months Unrealized Losses	4,106	7,036
12 Months or More Fair Value	15,517	13,429
12 Months or More Unrealized Losses	327	656
Total Fair Value	317,939	355,184
Total Unrealized Losses	4,433	7,692
US Government-sponsored Enterprises Debt Securities [Member]
Less than 12 Months Fair Value	57,666	51,657
Less than 12 Months Unrealized Losses	369	460
12 Months or More Fair Value	1,992	0
12 Months or More Unrealized Losses	8	0
Total Fair Value	59,658	51,657
Total Unrealized Losses	377	460
US States and Political Subdivisions Debt Securities [Member]
Less than 12 Months Fair Value	57,732	91,728
Less than 12 Months Unrealized Losses	765	2,526
12 Months or More Fair Value	4,838	1,999
12 Months or More Unrealized Losses	98	10
Total Fair Value	62,570	93,727
Total Unrealized Losses	863	2,536
Residential Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	142,716	154,397
Less than 12 Months Unrealized Losses	1,783	2,485
12 Months or More Fair Value	8,567	5,841
12 Months or More Unrealized Losses	218	202
Total Fair Value	151,283	160,238
Total Unrealized Losses	2,001	2,687
Commercial Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	42,997	43,309
Less than 12 Months Unrealized Losses	1,186	1,557
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	42,997	43,309
Total Unrealized Losses	1,186	1,557
Corporate Debt Securities [Member]
Less than 12 Months Fair Value	1,311	536
Less than 12 Months Unrealized Losses	3	6
12 Months or More Fair Value		5,476
12 Months or More Unrealized Losses		435
Total Fair Value	1,311	6,012
Total Unrealized Losses	3	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	120	113
12 Months or More Unrealized Losses	3	9
Total Fair Value	120	241
Total Unrealized Losses	$ 3	$ 11