Note 8 - Employee Benefit Plans - Fair Value Measurements (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Fair value, plan assets		$ 21,786	$ 23,428
Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		13,344	16,414
Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		8,442	7,014
Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Cash [Member]
Fair value, plan assets		1,917	4,454
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		1,917	4,454
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
Defined Benefit Plan, Equity Securities, US [Member]
Fair value, plan assets		8,782	9,892
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		8,782	9,892
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		0	0
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Defined Benefit Plan, Equity Securities, Non-US [Member]
Fair value, plan assets		471	106
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets		471	106
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets		0	0
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Equity Funds [Member]
Fair value, plan assets	[1]	2,174	1,962
Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets	[1]	2,174	1,962
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		50	51
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		50	51
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		202	231
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		202	231
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value, plan assets		0	0
Corporate Debt Securities [Member]
Fair value, plan assets	[2]	8,190	6,732
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair value, plan assets	[2]	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value, plan assets	[2]	8,190	6,732
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [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.