Note 6 - Stockholders' Equity and Dilutive Equity Instruments - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Balance at December 31, 2022 and 2021	$ 865,990	$ 701,769
Unrealized loss on note receivable	(132)	0
Balance at March 31, 2023 and 2022	873,413	689,742
AOCI Attributable to Parent [Member]
Balance at December 31, 2022 and 2021	8,576	2,668
Unrealized loss on note receivable	(132)	0
Balance at March 31, 2023 and 2022	8,254	2,471
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before reclassifications	$ (190)	$ (197)