Note 6 - Investment Securities - Investment Securities with Unrealized Losses Not Recognized in Income (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
US Government-sponsored Enterprises Debt Securities [Member]
Less than 12 Months Fair Value	$ 16,613,000	$ 57,927,000
Less than 12 Months Unrealized Losses	8,000	275,000
12 Months or More Fair Value	0	21,576,000
12 Months or More Unrealized Losses	0	263,000
Total Fair Value	16,613,000	79,503,000
Total Unrealized Losses	8,000	538,000
US States and Political Subdivisions Debt Securities [Member]
Less than 12 Months Fair Value	31,264,000	30,426,000
Less than 12 Months Unrealized Losses	145,000	123,000
12 Months or More Fair Value	1,215,000	8,276,000
12 Months or More Unrealized Losses	3,000	90,000
Total Fair Value	32,479,000	38,702,000
Total Unrealized Losses	148,000	213,000
Residential Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	44,381,000	118,978,000
Less than 12 Months Unrealized Losses	213,000	851,000
12 Months or More Fair Value	6,460,000	21,723,000
12 Months or More Unrealized Losses	66,000	638,000
Total Fair Value	50,841,000	140,701,000
Total Unrealized Losses	279,000	1,489,000
Commercial Mortgage Backed Securities [Member]
Less than 12 Months Fair Value	18,029,000	10,882,000
Less than 12 Months Unrealized Losses	151,000	123,000
12 Months or More Fair Value	0	0
12 Months or More Unrealized Losses	0	0
Total Fair Value	18,029,000	10,882,000
Total Unrealized Losses	151,000	123,000
Corporate Debt Securities [Member]
Less than 12 Months Fair Value	0	204,000
Less than 12 Months Unrealized Losses	0	6,000
12 Months or More Fair Value	5,205,000	5,155,000
12 Months or More Unrealized Losses	702,000	794,000
Total Fair Value	5,205,000	5,359,000
Total Unrealized Losses	702,000	800,000
Mutual Funds and Equity Securities [Member]
Less than 12 Months Fair Value	128,000	481,000
Less than 12 Months Unrealized Losses	2,000	21,000
12 Months or More Fair Value	116,000	264,000
12 Months or More Unrealized Losses	7,000	48,000
Total Fair Value	244,000	745,000
Total Unrealized Losses	9,000	69,000
Less than 12 Months Fair Value	110,415,000	218,898,000
Less than 12 Months Unrealized Losses	519,000	1,399,000
12 Months or More Fair Value	12,996,000	56,994,000
12 Months or More Unrealized Losses	778,000	1,833,000
Total Fair Value	123,411,000	275,892,000
Total Unrealized Losses	$ 1,297,000	$ 3,232,000