Net Loss (Gain) on Marketable Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Net Loss (Gain) on Marketable Securities
Unrealized losses (gains) on marketable equity securities	$ 5,542	$ (7,863)	$ 2,324	$ (21,819)
Realized (gains) losses on marketable equity securities	(255)	(548)	(524)	1,624
Realized losses on available-for-sale debt securities	6	23	17	23
Net loss (gain) on marketable securities	$ 5,293	$ (8,388)	$ 1,817	$ (20,172)