Note 8 - Benefit Plans - Defined Benefit Plans Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in benefit obligation
Benefit obligation at beginning of year	$ 25,258	$ 24,790
Service cost - benefits earned during the period	65	57	$ 48
Interest cost on projected benefit obligation	965	988	951
Recognized actuarial loss	3,755	1,288
Benefits paid	(1,657)	(1,865)
Benefit obligation at end of year	28,386	25,258	24,790
Changes in plan assets
Fair value of plan assets at beginning of year	15,791	15,865
Actual return on assets	2,413	1,291
Employer contributions	5,598	500
Benefits paid	(1,657)	(1,865)
Fair value of plan assets at end of year	22,145	15,791	$ 15,865
Funded status at end of year	(6,241)	(9,467)
Amounts recognized in consolidated balance sheet
Long-term pension liability	(8,319)	(9,467)
	(6,241)	(9,467)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	10,903	9,819
Other Assets [Member]
Amounts recognized in consolidated balance sheet
Other assets	2,181
Other Current Liabilities [Member]
Amounts recognized in consolidated balance sheet
Other current liabilities	$ (103)