Note 5 - Stockholders' Equity and Dilutive Equity Instruments - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Balance at March 31, 2024 and 2023	$ 1,055,153	$ 873,413	$ 1,037,697	$ 865,990
Unrealized gain (loss) on note receivable	73	(184)	153	(316)
Balance at June 30, 2024 and 2023	1,078,987	892,527	1,078,987	892,527
AOCI Attributable to Parent [Member]
Balance at March 31, 2024 and 2023	5,209	8,254	5,266	8,576
Unrealized gain (loss) on note receivable	73	(184)	153	(316)
Balance at June 30, 2024 and 2023	5,062	4,566	5,062	4,566
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Before reclassifications	$ (220)	$ (3,504)	$ (357)	$ (3,694)