Note 13 - Fair Value Measurements - Available for Sale Investment Securities Measured At Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available for Sale Debt Securities - Estimated Fair Value	$ 379,979	$ 423,318
Equity Securities - Fair Value	1,573	935
Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	379,979	423,318
Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
US Government-sponsored Enterprises Debt Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	33,824	43,208
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	33,824	43,208
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
US States and Political Subdivisions Debt Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	103,429	114,249
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	103,429	114,249
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Residential Mortgage Backed Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	172,838	193,393
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	172,838	193,393
Residential Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Commercial Mortgage Backed Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	46,909	49,352
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	46,909	49,352
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Asset-backed Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	15,499	15,574
Asset-backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Asset-backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	15,499	15,574
Asset-backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Corporate Debt Securities [Member]
Available for Sale Debt Securities - Estimated Fair Value	7,480	7,542
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available for Sale Debt Securities - Estimated Fair Value	7,480	7,542
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available for Sale Debt Securities - Estimated Fair Value	0	0
Mutual Funds and Equity Securities [Member]
Equity Securities - Fair Value	1,573	935
Mutual Funds and Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Equity Securities - Fair Value	1,573	935
Mutual Funds and Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Equity Securities - Fair Value	0	0
Mutual Funds and Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Equity Securities - Fair Value	$ 0	$ 0