Other Changes in Plan Assets And Benefit Obligations Recognized in OCI (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2017	May 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ 2,926	$ (3,858)
Amortization of net loss	559	434
Total recognized in other comprehensive income (loss)	3,485	(3,424)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	$ 3,157	$ (3,535)