Note 6 - Stockholders' Equity - Schedule of Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Balance Beginning	$ 1,980,065		$ 1,968,104	$ 1,992,836		$ 1,978,967
Balance Ending	2,038,282	$ 1,980,065		1,977,770	$ 1,992,836
Changes in fair value of derivative contracts designated as hedge transactions
Balance Beginning	1,817	8,305	13,708	20,910	15,678	9,162
Changes in fair value of derivative contracts	3,872	(4,545)	(3,971)	(5,265)	7,445	8,665
Gains and deferred gains transferred from accumulated other comprehensive income	(701)	(1,943)	(1,432)	(6,119)	(2,213)	(2,149)
Balance Ending	4,988	1,817	8,305	9,526	20,910	15,678
Adjustments For Pension Plans
Balance Beginning	(7,871)	(7,871)	(7,871)	(6,714)	(6,714)	(6,714)
Changes in fair value of derivative contracts			0	0	0	0
Gains and deferred gains transferred from accumulated other comprehensive income		0	0	0	0	0
Balance Ending	(7,871)	(7,871)	(7,871)	(6,714)	(6,714)	(6,714)
Accumulated Distributions in Excess of Net Income
Balance Beginning	(6,054)	434	5,837	14,196	8,964	2,448
Changes in fair value of derivative contracts	3,872	(4,545)	(3,971)	(5,265)	7,445	8,665
Gains and deferred gains transferred from accumulated other comprehensive income	(701)	(1,943)	(1,432)	(6,119)	(2,213)	(2,149)
Balance Ending	$ (2,883)	$ (6,054)	$ 434	$ 2,812	$ 14,196	$ 8,964