Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Temporarily impaired securities, less than 12 months, fair value	$ 77,054,000	$ 39,454,000
Temporarily impaired securities, less than 12 months unrealized loss	509,000	762,000
Temporarily impaired securities, 12 months or more fair value	72,369,000	281,626,000
Temporarily impaired securities, 12 months or more unrealized loss	265,000	7,365,000
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	27,231,000	17,730,000
Temporarily impaired securities, less than 12 months unrealized loss	211,000	216,000
Temporarily impaired securities, 12 months or more fair value	71,778,000	259,992,000
Temporarily impaired securities, 12 months or more unrealized loss	217,000	6,450,000
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value		16,882,000
Temporarily impaired securities, less than 12 months unrealized loss		352,000
Temporarily impaired securities, 12 months or more fair value	591,000	20,758,000
Temporarily impaired securities, 12 months or more unrealized loss	48,000	814,000
Commercial Mortgage Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	49,823,000
Temporarily impaired securities, less than 12 months unrealized loss	298,000
Temporarily impaired securities, 12 months or more fair value
Temporarily impaired securities, 12 months or more unrealized loss
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value		4,842,000
Temporarily impaired securities, less than 12 months unrealized loss		194,000
Temporarily impaired securities, 12 months or more fair value		876,000
Temporarily impaired securities, 12 months or more unrealized loss		$ 101,000