Note 11 - Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Assets measured at fair value		$ 232,494	$ 175,174
Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		232,494	175,174
Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
US Government Agencies Debt Securities [Member]
Assets measured at fair value		36,474	10,354
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		36,474	10,354
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
US States and Political Subdivisions Debt Securities [Member]
Assets measured at fair value		53,850	59,428
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		53,850	59,428
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
Residential Mortgage Backed Securities [Member]
Assets measured at fair value		105,224	69,604
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		105,224	69,604
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
Corporate Debt Securities [Member]
Assets measured at fair value		6,968	16,116
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		6,968	16,116
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
Commercial Mortgage Backed Securities [Member]
Assets measured at fair value		26,148	15,514
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value		26,148	15,514
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value
Other Investment Securities [Member]
Assets measured at fair value	[1]	3,830	4,158
Other Investment Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value	[1]
Other Investment Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value	[1]	3,830	4,158
Other Investment Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets measured at fair value	[1]

[1] Principally consists of residential mortgage-backed securities issued by both by governmental and nongovernmental agencies securities.