Note 11 - Stockholders' Equity - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Balance at December 31	$ 865,990	$ 701,769	$ 823,272
Unrealized gain (loss) on note receivable	213	(496)	0
Balance at December 31	1,037,697	865,990	701,769
AOCI Attributable to Parent [Member]
Balance at December 31	8,576	2,668	(804)
Unrealized gain (loss) on note receivable	213	(496)	0
Balance at December 31	5,266	8,576	2,668
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before reclassifications	$ (3,523)	$ 6,404	$ 3,472