Note 4 - Fair Value of Financial Instruments - Derivative Instruments in Other Comprehensive Income (Loss) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Balance in Other comprehensive income (loss) beginning of period	$ 1,515,410
Balance in Other comprehensive income (loss) end of period	1,571,803
Cross Currency Interest Rate Contract [Member] | Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member]
Balance in Other comprehensive income (loss) beginning of period	0
Gain or (loss) recognized in Other comprehensive income (loss)	(2,790)
Amount reclassified from Other comprehensive income (loss) into earnings	(758)
Balance in Other comprehensive income (loss) end of period	$ (3,548)