Reconciliation of Financial Security Plan Benefit Obligation (Detail) (Financial Security Defined Benefit Plans, USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Financial Security Defined Benefit Plans
Change in projected benefit obligation
Benefit obligation at beginning of year	$ 48,091	$ 43,959
Service cost	2,147	2,213	1,673
Interest cost	2,517	2,311	2,289
Recognized actuarial loss (gain)	4,366	2,347
Benefits paid	(2,891)	(2,739)
Benefit obligation at end of year	54,230	48,091	43,959
Funded status at end of year	$ (54,230)	$ (48,091)