Note 8 - Benefit Plans - Defined Benefit Plans Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Benefit obligation at beginning of year	$ 28,470	$ 27,125
Service cost - benefits earned during the period	152	117
Interest cost on projected benefit obligation	863	1,084
Actuarial loss	5,383	3,835
Benefits paid	(1,753)	(3,691)
Benefit obligation at end of year	33,115	28,470	$ 27,125
Fair value of plan assets at beginning of year	19,939	19,980
Actual return on assets	462	3,547
Employer contributions	103	103
Benefits paid	(1,750)	(3,691)
Fair value of plan assets at end of year	18,754	19,939	19,980
Funded status at end of year	(14,361)	(8,531)
Other assets	314	1,825
Other current liabilities	(101)	(103)
Long-term pension liability	(14,574)	(10,253)
Net amount recognized	(14,361)	(8,531)
Net actuarial loss	15,656	10,828
Pension Plan [Member]
Benefit obligation at beginning of year	18,114	18,317
Service cost - benefits earned during the period	0	0
Interest cost on projected benefit obligation	541	721	675
Actuarial loss	1,773	2,664
Benefits paid	(1,650)	(3,588)
Benefit obligation at end of year	18,778	18,114	18,317
Fair value of plan assets at beginning of year	19,939	19,980
Actual return on assets	462	3,547
Employer contributions	0	0
Benefits paid	(1,647)	(3,588)
Fair value of plan assets at end of year	18,754	19,939	19,980
Funded status at end of year	(24)	1,825
Other assets	314	1,825
Other current liabilities	0	0
Long-term pension liability	(338)	0
Net amount recognized	(24)	1,825
Net actuarial loss	8,227	6,312
Supplemental Employee Retirement Plan [Member]
Benefit obligation at beginning of year	10,356	8,808
Service cost - benefits earned during the period	152	117	108
Interest cost on projected benefit obligation	322	363	295
Actuarial loss	3,610	1,171
Benefits paid	(103)	(103)
Benefit obligation at end of year	14,337	10,356	8,808
Fair value of plan assets at beginning of year	0	0
Actual return on assets	0	0
Employer contributions	103	103
Benefits paid	(103)	(103)
Fair value of plan assets at end of year	0	0	$ 0
Funded status at end of year	(14,337)	(10,356)
Other assets	0	0
Other current liabilities	(101)	(103)
Long-term pension liability	(14,236)	(10,253)
Net amount recognized	(14,337)	(10,356)
Net actuarial loss	$ 7,429	$ 4,516