Investment (Income), Net (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Net Investment Income [Line Items]
Interest (income)	$ (1,780)	$ (2,179)	$ (4,924)	$ (6,039)
(Gain) loss on sale of marketable securities	(4,646)	(2,926)	(7,070)	(7,518)
Other-than-temporary impairment on securities		44	161	608
Dividend (income)	(1,325)	(1,256)	(1,817)	(1,706)
Investment (income), net	$ (7,751)	$ (6,317)	$ (13,650)	$ (14,655)