Other Changes in Plan Assets And Benefit Obligations Recognized in OCI (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss)	$ (12,899)	$ 1,606
Amortization of prior service cost	70	350
Total recognized in other comprehensive income	(12,829)	1,956
Total recognized in net periodic benefit cost and other comprehensive income	$ (12,497)	$ 1,145