Note 19. Retirement Plan (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Aug. 19, 2011	May 31, 2012	May 31, 2011	May 31, 2010
United States [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.4	$ 1.0	$ 1.0	$ 0.9
Canada [Member]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0.1	$ 0.1	$ 0.1	$ 0.1