Note 8 - Employee Benefit Plans - Fair Value Measurements (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Dec. 31, 2015
Fair value, plan assets		$ 17,038	$ 16,131
Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		10,484	11,075
Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		6,554	5,056
Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Cash [Member]
Fair value, plan assets		207	876
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		207	876
Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		0	0
Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Equity Securities US Companies [Member]
Fair value, plan assets		9,195	9,600
Equity Securities US Companies [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		9,195	9,600
Equity Securities US Companies [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		0	0
Equity Securities US Companies [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Equity Securities International Companies [Member]
Fair value, plan assets		116	404
Equity Securities International Companies [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		116	404
Equity Securities International Companies [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		0	0
Equity Securities International Companies [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Equity Funds [Member]
Fair value, plan assets	[1]	966	195
Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets	[1]	966	195
Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets	[1]	0	0
Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets	[1]	0	0
US Government Corporations and Agencies Securities [Member]
Fair value, plan assets		53	104
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		0	0
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		53	104
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
US States and Political Subdivisions Debt Securities [Member]
Fair value, plan assets		230	233
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		230	233
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Corporate Debt Securities [Member] | External Credit Rating, Investment Grade [Member]
Fair value, plan assets	[2]	6,271	4,719
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | External Credit Rating, Investment Grade [Member]
Fair value, plan assets	[2]	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | External Credit Rating, Investment Grade [Member]
Fair value, plan assets	[2]	6,271	4,719
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | External Credit Rating, Investment Grade [Member]
Fair value, plan assets	[2]	$ 0	$ 0

[1] This category comprises actively managed equity funds invested in large-cap and mid-cap U.S. companies.

[2] This category represents investment grade bonds of U.S. issuers from diverse industries.