Note 8 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 0	$ 1,100	$ 0
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan, Plan Assets, Contributions by Employer	400	$ 2,100	1,200	$ 2,900
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year	400		400
Defined Benefit Plan, Benefit Obligation, Ending Balance	$ 21,000		$ 21,000		$ 21,400