Note 15 - Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Nov. 30, 2022	Nov. 30, 2021	Aug. 31, 2021	Nov. 30, 2022	Nov. 30, 2021
Balance	$ 4,563,182	$ 4,385,756	$ 4,465,313	$ 4,441,366	$ 4,465,313
Other comprehensive loss	(42,240)	(48,672)		(105,057)	(150,093)
Balance	4,483,146	4,472,989	4,385,756	4,483,146	4,472,989
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Balance		(2,030)	54,413		54,413
Other comprehensive loss	(24,080)		(56,443)
Balance	(26,110)		(2,030)	(26,110)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Balance		(77,702)	(75,177)		(75,177)
Other comprehensive loss	(17,643)		(2,525)
Balance	(95,345)		(77,702)	(95,345)
Unrealized Loss on Available for Sale Debt Securities [Member]
Balance		$ (79,732)	(20,764)		$ (20,764)
Other comprehensive loss	(41,723)		(58,968)
Balance	$ (121,455)		$ (79,732)	$ (121,455)