Note 4 - Securities - Securities in a Continuous Loss Position (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Temporarily impaired securities, less than 12 months, fair value	$ 7,876,000	$ 39,454,000
Temporarily impaired securities, less than 12 months unrealized loss	81,000	762,000
Temporarily impaired securities, 12 months or more fair value	162,263,000	281,626,000
Temporarily impaired securities, 12 months or more unrealized loss	734,000	7,365,000
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	7,302,000	17,730,000
Temporarily impaired securities, less than 12 months unrealized loss	16,000	216,000
Temporarily impaired securities, 12 months or more fair value	161,285,000	259,992,000
Temporarily impaired securities, 12 months or more unrealized loss	733,000	6,450,000
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	574,000	16,882,000
Temporarily impaired securities, less than 12 months unrealized loss	65,000	352,000
Temporarily impaired securities, 12 months or more fair value		20,758,000
Temporarily impaired securities, 12 months or more unrealized loss		814,000
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	978,000	876,000
Temporarily impaired securities, 12 months or more unrealized loss	$ 1,000	$ 101,000