Note 6 - Stockholders' Equity - Schedule of Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023
Balance Beginning	$ 1,958,630	$ 1,968,104	$ 1,992,157	$ 1,978,967
Balance Ending	1,980,065	1,958,630	1,992,836	1,992,157
Changes in fair value of derivative contracts designated as hedge transactions [Member]
Balance Beginning	8,305	13,708	15,678	9,162
Changes in fair value of derivative contracts	(4,545)	(3,971)	7,445	8,665
Gains and deferred gains transferred from accumulated other comprehensive income	(1,943)	(1,432)	(2,213)	(2,149)
Balance Ending	1,817	8,305	20,910	15,678
Adjustments For Pension Plans [Member]
Balance Beginning	(7,871)	(7,871)	(6,714)	(6,714)
Changes in fair value of derivative contracts		0	0	0
Gains and deferred gains transferred from accumulated other comprehensive income	0	0	0	0
Balance Ending	(7,871)	(7,871)	(6,714)	(6,714)
Accumulated Distributions in Excess of Net Income [Member]
Balance Beginning	434	5,837	8,964	2,448
Changes in fair value of derivative contracts	(4,545)	(3,971)	7,445	8,665
Gains and deferred gains transferred from accumulated other comprehensive income	(1,943)	(1,432)	(2,213)	(2,149)
Balance Ending	$ (6,054)	$ 434	$ 14,196	$ 8,964