Note 18 - Retirement Plans - Fair Values of the Company's Pension Plan Assets by Asset Category (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair value of plan assets	$ 39,524	$ 39,135
Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	37,326	36,967
Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets	2,198	2,168
Equity Securities U.S. Companies [Member]
Fair value of plan assets	15,567	13,547
Equity Securities U.S. Companies [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	15,567	13,547
Equity Securities International Companies [Member]
Fair value of plan assets	8,647	7,377
Equity Securities International Companies [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	8,647	7,377
Fixed Income Funds [Member]
Fair value of plan assets	13,432	13,375
Fixed Income Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	11,234	11,207
Fixed Income Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Fair value of plan assets	2,198	2,168
Commodities [Member]
Fair value of plan assets	1,878	2,962
Commodities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets	$ 1,878	2,962
US Treasury Securities [Member]
Fair value of plan assets		1,874
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair value of plan assets		$ 1,874