Investment Expense (Income), Net (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Other Income And Expenses [Abstract]
Interest (income)	$ (828)	$ (1,297)	$ (1,732)	$ (2,191)
Net loss (gain) on marketable securities	8,520	(2,037)	8,134	(4,897)
Dividend (income)	(659)	(405)	(1,802)	(1,104)
Investment expense (income), net	$ 7,033	$ (3,739)	$ 4,600	$ (8,192)