Note 5 - Fair Value of Financial Instruments - Effect of Cash Flow Hedge on Statement of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Balance in Other comprehensive income (loss) beginning of period	$ 1,959,855	$ 1,556,811	$ 1,941,437	$ 1,515,410
Balance in Other comprehensive income (loss) end of period	1,972,356	1,575,351	1,972,356	1,575,351
Cross Currency Swap [Member] | Designated as Hedging Instrument [Member] | Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member]
Balance in Other comprehensive income (loss) beginning of period	766	0	3,366	0
Gain or (loss) recognized in Other comprehensive income (loss)	251	(2,790)	(6,643)	(2,790)
Amount reclassified from Other comprehensive income (loss) into earnings	(2,945)	(758)	1,349	(758)
Balance in Other comprehensive income (loss) end of period	$ (1,928)	$ (3,548)	$ (1,928)	$ (3,548)