Note 3 - Investment Securities - Investment Securities With Unrealized Losses Not Recognized In Income (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Less than 12 Months Fair Value	$ 341,755	$ 218,898
Less than 12 Months Unrealized Losses	7,036	1,399
12 Months or More Fair Value	13,429	56,994
12 Months or More Unrealized Losses	656	1,833
Total Fair Value	355,184	275,892
Total Unrealized Losses	7,692	3,232
US Government-sponsored Enterprises Debt Securities [Member]
Less than 12 Months Fair Value	51,657	57,927
Less than 12 Months Unrealized Losses	460	275
12 Months or More Fair Value		21,576
12 Months or More Unrealized Losses		263
Total Fair Value	51,657	79,503
Total Unrealized Losses	460	538
US States and Political Subdivisions Debt Securities [Member]
Less than 12 Months Fair Value	91,728	30,426
Less than 12 Months Unrealized Losses	2,526	123
12 Months or More Fair Value	1,999	8,276
12 Months or More Unrealized Losses	10	90
Total Fair Value	93,727	38,702
Total Unrealized Losses	2,536	213
Residential Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	154,397	118,978
Less than 12 Months Unrealized Losses	2,485	851
12 Months or More Fair Value	5,841	21,723
12 Months or More Unrealized Losses	202	638
Total Fair Value	160,238	140,701
Total Unrealized Losses	2,687	1,489
Commercial Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	43,309	10,882
Less than 12 Months Unrealized Losses	1,557	123
12 Months or More Fair Value	0
12 Months or More Unrealized Losses	0
Total Fair Value	43,309	10,882
Total Unrealized Losses	1,557	123
Corporate Debt Securities [Member]
Less than 12 Months Fair Value	536	204
Less than 12 Months Unrealized Losses	6	6
12 Months or More Fair Value	5,476	5,155
12 Months or More Unrealized Losses	435	794
Total Fair Value	6,012	5,359
Total Unrealized Losses	441	800
Mutual Funds and Equity Securities [Member]
Less than 12 Months Fair Value	128	481
Less than 12 Months Unrealized Losses	2	21
12 Months or More Fair Value	113	264
12 Months or More Unrealized Losses	9	48
Total Fair Value	241	745
Total Unrealized Losses	$ 11	$ 69